255 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) ISSN (Print) 2313-4410, ISSN (Online) 2313-4402 © Global Society of Scientific Research and Researchers http://asrjetsjournal.org/ Hamltonian Connectedness and Toeplitz Graphs Hassan Zafara, Naveed Akhter b*, Muhammad Kamran Jamilc, Faisal Nadeemd aNational College of Business & Administration, DHA Campus, Lahore 54590, Pakistan bGovt. Dyal Singh College, Lahore 54590 , Pakistan cRiphah Institute of Computing and Applied Sciences (RICAS) Riphah International University, Lahore 54590, Pakistan. , Pakistan dDepartment of Mathematics, COMSATS, Institute of Information and Technology, Lahore 54590, Pakistan aEmail: hassanxfr@hotmail.com bEmail: akhtarnaweed@yahoo.com cEmail: m.kamran.sms@gmail.com dEmail: faisal.nadeem@ciitlahore.edu.pk Abstract A square matrix of order n is called Toeplitz matrix if it has constant elements along all diagonals parallel to the main diagonal and a graph is called Toeplitz graph if its adjacency matrix is Toeplitz. In this paper we proved that the Toeplitz graphs 2,3, tnT , for 28n  and 8 4 2 n t    are Hamiltonian connected. Keywords: Hamiltonian graph; Hamiltonian connected; Toeplitz graph; Toeplitz matrix; Hamiltonian path. 1. Introduction A square matrix of order n is called Toeplitz matrix if it has constant elements along all diagonals parallel to the main diagonal. A simple undirected graph nT with vertex set  1,2,3, ,n is called a Toeplitz graph if its adjacency matrix is Toeplitz. A Toeplitz graph is uniquely defined by the first row of its adjacency matrix. The first row of adjacency matrix of a Toeplitz graph is always a sequence of 0’s and 1’s. If the 1’s in that sequence places at 1 2 31, 1, 1, , 1kt t t t    positions with 1 2 31 ,kt t t t n      we write 1 2 3, , , ,n n kT T t t t t . In a Toeplitz graph 1 2 3, , , ,n kT t t t t two vertices a and b are connected by an edge if and only if  1 2 3, , , , ka b t t t t  . ------------------------------------------------------------------------ * Corresponding author. http://asrjetsjournal.org/ mailto:example@yahoo.com American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 33, No 1, pp 255-268 256 A graph G of order n is called Hamiltonian if it contains a cycle of order n . A graph G of order n is called traceable if it contains a path of order n and such a path is called Hamiltonian path. The graph G is called Hamiltonian connected if for any pair of distinct vertices a and b of G , there exists a Hamiltonian path with ends a and b . Every Hamiltonian connected graph is Hamiltonian. Connectedness, bipartiteness, colourbality and planarity of Toeplitz graphs are discussed in [1, 2, 3, 4]. Some of the Hamiltonian properties of undirected Toeplitz graphs were discussed in [1] and [5]. The Hamiltonian properties of directed Toeplitz graphs were studied in [6, 7]. S. Malik and T. Zamfirescu investigated Hamiltonian properties of Toeplitz graphs in [8]. M. F. Nadeem Ayesha Shabbir and Tudor Zamfirescu complete the picture of Toeplitz graphs 1 2, , 1,3,n nT t t T t and 1,5, tnT in [9]. In this paper we proved that the Toeplitz graphs 2,3, tnT are Hamiltonian connected for 28n  and 8 4 2 n t    . Suppose T is a Toeplitz graph and , , , ,l m k q n are its vertices. If l m , then  , 1,P l l m is a path with ends l and 1l  that contains all vertices, , 1, 2, ,m m m l  . If m l then  , 1,P l l m a path with ends l and 1l  that contains all vertices, , 1, 2, ,l l l m   . The path  ,P l m has end vertices l and m and contains all vertices, , 1, 2, ,l l l m   except vertices 1l  and 1m . The path  ,H l m has ends l and m and contains all vertices , 1, 2, ,l l l m   . The path  ' , ,P l m k has end vertices l and m , and contains all vertices , 1, 2, ,l l l m   except vertex  1, 1k l m   . The path  ,y xH l m has ends x ,y and contains vertices , 1, 2, ,l l l m   . The path  ,y xh l m has ends x and y contains all vertices , 1, 2, ,l l l m   such that 5 , 5l x y m    . 2. Preliminaries Lemma 2.1 The Toeplitz graph 2,3nT , n ≥ 6 admits Hamiltonian path  1,2,P n and  1, ,1P n n . Proof. The Toeplitz graph 2 2,3nT has he following Hamiltonian path  1,2,P n . “1,3,5, ,2 7,n 2n 5, 2n 2,2n,2n 3,2n 1,2n 4,2n 6, 6,4,2.     ” The Toeplitz graph 2 1 2,3nT  the Hamiltonian path “ 1,3,5, 2 5,2 3,2 ,2 2,n n n n   2 1,2 1,n n  2 4,n  2 6, 6,4,2n ” that connects 1 and 2. Due to symmetry of the Toeplitz graphs 2,3nT has Hamiltonian path  1, ,1P n n . The Hamiltonian paths connecting 1 and 2 are shown in Fig. 1 and Fig. 2. Corollary 2.2 (a). In Toeplitz graphs 2,3nT , if l < m, then  , 1,mP l l  exists for 5.m l  (b). In Toeplitz graphs 2,3nT , if l > m, then  , 1,mP l l  exists for 4.l m  American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 33, No 1, pp 255-268 257 Figure 1: Hamiltonian Path with ends 1 and 2 Figure 2: Hamiltonian Path with ends 1 and 2 Lemma 2.3. The Toeplitz graph 2,3nT for 8n  contains the path  1, .P n Proof. We divide the proof in following four cases. Case 1. If  0 mod 4n  , then 4n k for 2.k  The required path is shown in Fig. 3. Figure 3: Path with ends 1 and 4k containing all vertices except 2 and 4 1k  Case 2. If  1 mod 4 ,n  then n = 4k + 1 for k _ 2. The path that connects 1 with 4k + 1 and contains all the vertices in the Toeplitz graph 4 1 2,3kT  except 2 and 4k is “1,4,6,3,5,8,10,7, ,4 6,4 9,4 7,k k k    4k 4, 4k 2,4k 5,4k 3,4k 1,4k 1     ” and is shown in Fig. 4. Case 3. If n = 2 (mod 4), then n = 4k + 2 for 2n  . The path that connects 1 with 4k + 2 and contains all the vertices in the Toeplitz graph 4 2 2,3kT  , except 2 and 4k+1 is 1,3,5,7,4,6,8,10,12,9,11,14,16,13,15,18, 4k 5 4 2,4 ,4 3,4 1,4 2k k k k k    " and is shown in Fig. 5. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 33, No 1, pp 255-268 258 Figure 4: Path with ends 1 and 4k + 1 containing all vertices except 2 and 4k Case 4. If n = 3 (mod 4), then n = 4k + 3 for 2n  . The path that connects 1 with 4k + 3 and contains all the vertices in the Toeplitz graph 4 3 2,3kT  , except 2 and 4k + 2 is “1,3,5,7,4,6,9,11,8,10,13, 4k 5,4k 8  , 4 6,4 3,4 ,4 2,4 4,4 3,4 1,4 3k k k k k k k k       ” and is shown in Fig. 6. Figure 5: Path with ends 1 and 4k + 2 containing all vertices except 2 and 4k + 1 Figure 6: Path with ends 1 and 4k + 3 containing all vertices except 2 and 4k + 2 Corollary 2.4. The path  ,P l m exists in Toeplitz graphs 2,3nT for 7.m l  Lemma 2.5. The Toeplitz graph 2,3nT , for 6n  and 8n  admits a Hamiltonian path  1,H n . Proof. We will prove this result in five cases. Case 1. If n = 1 (mod 5) then n = 5k + 1 where k N . See Fig. 7 for a Hamiltonian path from 1 to 5k + 1. Figure 7: Hamiltonian path connecting 1 and 5k + 1 in 5 1 2,3kT  American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 33, No 1, pp 255-268 259 Case 2. The Hamiltonian path connecting 1 and 7 in 7 2,3T is shown in Fig. 8. If n = 2 (mod 5), then we can write n = 5k + 2 where .k N For any Toeplitz graph 5 2 2,3kT  for 2k  joining the path of Fig. 8 from 1 to 7 with the path of Fig. 7 from 7 to 5k + 2 we get the Hamiltonian path connecting 1 and 5k + 2. Figure 8: Hamiltonian path between 1 and 7 in 7 2,3T Case 3. The Hamiltonian path connecting 1 and 13 in Toeplitz graph 13 2,3T , is shown in Fig. 9. If n = 3 (mod 5), then we can write n = 5k+3 for any 2.k  The Hamiltonian path joining vertices 1 and 5k + 3 in any Toeplitz graph 5 3 2,3kT  for 3k  is obtained by joining the path of Fig. 9 with the path of Fig 7. Figure 9: Hamiltonian path connecting 1 and 13 in 13 2,3T Case 4. If n = 4 (mod 5), then n = 5k + 4 for .k N In the Toeplitz graph 9 2,3T the Hamiltonian path connecting 1 and 9 is shown in Fig. 10. The Hamiltonian path connecting 1 and 5k + 4 for any 2k  in the Toeplitz graphs 5 4 2,3kT  is obtained by joining the path of Fig. 10 with the path of Fig. 7. Figure 10: Hamiltonian path connecting 1 and 9 in 9 2,3T Case 5. If n = 0 (mod 5). The Hamiltonian path connecting 1 and 10 in Toeplitz graph 10 2,3T is shown in Fig. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 33, No 1, pp 255-268 260 11 while the Hamiltonian path connecting 1 and 5k for 3k  in the Toeplitz graphs 5 2,3kT is obtained by joining paths of Fig. 11 and Fig. 7. Corollary 2.6. In Toeplitz graphs 2,3nT , the Hamiltonian path  ,H l m exists for 5m l  and 7m l  . Figure 11: Hamiltonian path connecting 1 and 10 in 10 2,3T Corollary 2.7. The Toeplitz graph 2,3nT for n ≥ 9 and 11n  has a path with ends 1 and n that contains all vertices of the graph except vertices 2 and 3. Proof. The required path is “1, 4, H[4, n], n”. Lemma 2.8. The Toeplitz graphs 2,3nT for all n ≥ 7 has a paths  ' 1, ,2P n and  ' 1, , 1P n n  . Proof. The required paths for 7 2,3T and 10 2,3T are shown in Fig. 12. The required path for all other n is obtained by first connecting 1 with 3 and then connecting 3 with n using the Hamiltonian path of Lemma 2.5. Due to symmetry of Toeplitz graph there is a path with ends 1 and n that contains all vertices except n − 1. Figure 12: Path connecting 1 and n except 2 Corollary 2.9. In 2,3nT the path  ' , ,P l m k exists for m − l ≥ 6. Lemma 2.10. In 2,3nT for n ≥ 6 and 7n  7 the Hamiltonian paths  2 1,nH n and  1 1 1,nH n exists. Proof. In 6 2,3T the required Hamiltonian path is “ 2,5,3,1,4,6 ”. The path “ 2,5,7,4,1,3,6,8 ” is the required Hamiltonian path in 8 2,3T . The required Hamiltonian path in 9 2,3T is “ 2,4,1,3,6,8,5,7,9 ”. In 2,3nT for 9n  the required path is “  2,4,1,3,P' 3, ,4 ,n n ”. Lemma 2.11. In 2,3,nT t , n ≥ 20 and 4 ≤ t ≤ n − 11, the Hamiltonian path  1 1,xH n exists for all 2 x n  . American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 33, No 1, pp 255-268 261 Proof. The Hamiltonian paths between vertex 1 with all other vertices except 3n  4 7t n   are shown in Table 1. Table 1: Hamiltonian Path between 1 and other vertices. End Vertices Hamiltonian Path 1 – 2, (n ≥ 6) 1, P [1, 2, n], 2. 1 – 3, (n ≥ 10) 1, 4, 2, 5, P [5, 6, n], 6, 3. 1 – 4, (n ≥ 10) 1, 3, 6, P [5, 6, n], 5, 2, 4. 1 – 5, (n ≥ 11) 1, 3, 6, P [6, 7, n], 7, 4, 2, 5. 1 – x, (n ≥ 11) 6 ≤ x ≤ n − 5 1,  ' 1, 1,P x x , x + 1, P [x, x + 1, n], x. 1 – (n − 4), (n ≥ 14) 1, H[1, n − 5], n − 5, P [n − 5, n − 4, n], n − 4. 1 – (n − 2), (n ≥ 13) 1, H[1, n − 4], n − 4, n − 1, n − 3, n, n − 2. 1 – (n − 1), (n ≥ 13) 1, H[1, n − 4], n − 4, n − 2, n, n − 3, n − 1. 1 – n,(n ≥ 9) 1, H[1, n], n. Hamiltonian Path Between 1 and (n − 3) in 2,3,nT t , for different values of t is shown in Table 2. Table 2: Hamiltonian Path between 1 and n − 3. Condition on t Hamiltonian Path t = 4,(n ≥ 14) 1, H[1, n − 5], n − 5, n − 1, n − 4, n − 2, n, n − 3. t = 5, (n ≥ 14) 1, H[1, n − 5], n − 5, n, n − 2, n − 4, n − 1, n − 3. t = 6, (n ≥ 13) 1,  ' 1, 6, 7P n n  , n − 6, n, n − 2, n − 5, n − 7, n −4, n − 1, n − 3. t = 7, (n ≥ 14) 1, P l[1, n − 7, n − 8], n − 7, n, n − 2, n − 5, n − 8, n −6, n − 4, n − 1, n − 3. t = 8, (n ≥ 15) 1, P l[1, n − 8, n − 9], n − 8, n, n − 2, n − 5, n − 7, n −9, n − 6, n − 4, n − 1, n − 3. 9 ≤ t ≤ n − 11, (n ≥ 20) 1, H[1, n − t − 2], n − t − 2, P [n − t − 2, n − t − 1, n −5], n − t − 1, n − 1, n − 4, n − 2, n, n − 3. This path is shown in Fig. 13. Figure 13: Hamiltonian path with ends 1 and 3n  in 2,3, tnT when 4 6t n   Lemma 2.12. In 2,3,nT t , n ≥ 18 and 4 ≤ t ≤ n − 10, the Hamiltonian path  1 1,xH n exists for all 1 ≤ x ≤ n American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 33, No 1, pp 255-268 262 2x  . Proof. The Hamiltonian path of 2 with 1 is proved in Lemma 2.11 and with all other vertices except 3n  is shown in Table 3. Table 3: Hamiltonian Path of 2 with other vertices. End Vertices Hamiltonian Path 2 – 3, (n ≥ 9) 3, 1, 4, P [4, 5, n], 5, 2. 2 – 4, (n ≥ 10) 2, 5, P [5, 6, n], 6, 3, 1, 4. 2 – 5, (n ≥ 10) 2, 4, 1, 3, 6, P [5, 6, n], 5. 2 – 6, (n ≥ 10) 2, 4, 1, 3, 5, P [5, 6, n], 6. 2 – 7, (n ≥ 11) 2, 5, 3, 1, 4, 6, P [6, 7, n], 7. 2 – x, (n ≥ 14) 9 ≤ x ≤ n − 4 2,  1 2 1, 1xH x  , x − 1, P [x − 1, x, n], x. 2 – (n − 1), (n ≥ 13) 2,  5 2 1, 5nH n  , n − 5, n − 3, n, n − 2, n − 4, n − 1. 2 – (n − 2), (n ≥ 12) 2,  4 2 1, 4nH n  , n − 4, n − 1, n − 3, n, n − 2. 2 – n, (n ≥ 8) 2,  2 1,nH n , n. The Hamiltonian path of 2 with 3n  for 4 4 10t n   is shown in Table 4. Table 4: Hamiltonian Path of 2 with 3n  Condition on t Hamiltonian Path t = 4, (n ≥ 13) 2,  5 2 1, 5nH n  , n − 5, n − 1, n − 4, n − 2, n, n − 3. t = 5, ( 13n  ) 2,  5 2 1, 5nH n  , n − 5, n, n − 2, n − 4, n − 1, n − 3. t = 6, ( 16n  )  2,4,1,3, 3, 6 , 6, , 2, 5, 7, 4, 1, 3P n n n n n n n n n        t = 7, (n ≥ 17) 2, 4, 1, 3, P [3, n − 7], n − 7, n, n − 2, n − 5, n − 8, n −6, n − 4, n − 1, n − 3. 8 ≤ t ≤ n − 10, (n ≥ 18) 2,  2 2 1, 2n tH n t    , n − t − 2, P [n − t − 2, n − t −2 1, n − 5], n − t − 1, n − 1, n − 4, n − 2, n, n − 3. Lemma 2.13. In 2,3,nT t , n ≥ 20 and 4 ≤ t ≤ n − 11, the Hamiltonian path  3 1,xH n exists for all 1 ≤ x ≤ n and 3x  . Proof. The concerned Hamiltonian path of 3 with 1 and 2 are shown in Lamma's 2.11 and 2.12 respectively. Hamiltonian path of 3 with 4 is shown in Table 5. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 33, No 1, pp 255-268 263 Table 5: Hamiltonian Path of 3 with 4 Condition on t Hamiltonian Path 4,t   10n   3,1,5, 5,6, ,6,2,4.P n 5,t   11n   3.5,2,7, 6,7, ,6,1,4.P n 6,t   14n   3,5,2,8,6,9, 9,10, ,10,7,1,4.P n 7,t   14n   3,1,8,6,9, 9,10, ,10,7,1,4.P n t = 8, n ≥ 20 3, 1, 9, 7, 15, P [15, 16, n], 16, 13, 11, 14, 12, 10, 2, 5, 8, 6, 4. 9 ≤ t ≤ n − 7 t = 1 (mod 2) (n ≥ 16)  3,1, 1, 2, , 3, 2, 3, , 2,2,5,7, , t 4, t 1, t 3, ,8,6,4.t t t t P t t n t         10 ≤ t ≤ n − 7 t = 0 (mod 2) (n ≥ 17) 3, 1, t + 1, t − 2, t − 5, t − 7, . . . , 5, 2, t + 2, P [t + 2, t +3, n], t + 3, t, t − 3, t − 1, t − 4, t − 6, . . . , 8, 6, 4. The Hamiltonian path between 3 and 5 for 4 ≤ t ≤ n − 8 is shown in Table 6. Table 6: Hamiltonian Path of 3 with 5 Condition on t Hamiltonian Path t = 4, (n ≥ 11) 3, 1, 4, 7, P [6, 7, n], 6, 2, 5. t = 0 (mod 2) 6 ≤ t ≤ n − 7 (n ≥ 13) 3, 1, t + 1, t − 1, t − 3, . . . , 7, 4, 6, 8, . . . , t, t + 3, P [t +2, t + 3, n], t + 2, 2, 5. t = 1 (mod 2) 5 ≤ t ≤ n − 8 (n ≥ 13) 3, 1, t + 1, t + 4, P [t + 3, t + 4, n], t + 3, t, t −2, . . . , 7, 4, 6, 8, . . . , t − 1, t + 2, 2, 5. The Hamiltonian paths of 3 with vertices in the set  6,7,8, ,n except 3n  are shown in Table 7. Table 7: Hamiltonian Path of 3 with 5. End Vertices Hamiltonian Path 3 – 6, (n ≥ 10) 3, 1, 4, 2, 5, P [5, 6, n], 6. 3 – 7, (n ≥ 14) 3, 1, 4, 2, 5,  7 5 5,H n , 7. 3 8 ,  14n  3, 1, 4, 2, 5,  8 5 5,H n , 8. 3 – 9, (n ≥ 15) 3, 1, 4, 2, 5,  9 5 5,H n , 9. 3 – 10, (n ≥16) 3, 1, 4, 2, 5,  10 5 5,H n , 10. 3 – x, (n ≥ 16) 11 ≤ x ≤ n − 5 3, 1, 4, 2, 5, 'P [5, x + 1, x], x + 1, P [x, x + 1, n], x. 3 – n, (n ≥ 17) 3, 1, 4, 2, 5, H[5, n], n. 3 – (n − 1), (n ≥ 13) 3, 1, 4, 2, 5, 'P [5, n − 2, n − 3], n − 2, n, n − 3, n − 1. 3 – (n − 2), (n ≥ 17) 3, 1, 4, 2, 5, H[5, n − 4], n − 4, n − 1, n − 3, n, n − 2. 3 – (n − 4), n ≥ 18 3, 1, 4, 2, 5, H[5, n−5], n−5, n−2, n, n−3, n−1, n−4. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 33, No 1, pp 255-268 264 The Hamiltonian path between 3 and 3n  for 4 7t n   is given in the Table 8. Table 8: Hamiltonian Path between 3 and 3n  Condition on t Hamiltonian Path t = 4, (n ≥ 18) 3, 1, 4, 2, 5, H[5, n − 5], n − 5, n − 1, n − 4, n − 2, n, n − 3 t = 5, (n ≥ 18) 3, 1, 4, 2, 5, H[5, n − 5], n − 5, n, n − 2, n − 4, n − 1, n − 3. t = 6, (n ≥ 17) 3, 1, 4, 2, 5, 'P [5, n − 6, n − 7], n − 6, n, n − 2, n − 5, n −7, n − 4, n − 1, n − 3. t = 7, (n ≥ 18) 3, 1, 4, 2, 5, 'P [5, n − 7, n − 8], n − 7, n, n − 2, n − 5, n − 8, n − 6, n − 4, n − 1, n − 3. t = 8, (n ≥ 19) 3, 1, 4, 2, 5, 'P [5, n − 8, n − 9], n − 8, n, n − 2, n − 5, n −7, n − 9, n − 6, n − 4, n − 1, n − 3. 9 ≤ t ≤ n − 11, (n ≥ 20) 3, 1, 4, 2, 5, 'P [5, n − t, n − t − 1], n − t, P [n − t, n − t −1, n − 5], n − t − 1, n − 1, n − 4, n − 2, n, n − 3. Lemma 2.14. In 2,3,nT t , n ≥ 24 and 4 ≤ t ≤ n − 11, the Hamiltonian path 5 xH [1, n] exists for all 1 ≤ x ≤ n and 5.x  Proof. The Hamiltonian path of 5 with vertices 1, 2 and 3 is already shown. The Hamiltonian path of vertex 4 with 5 for different values of t is given in Table 9. Table 9: Hamiltonian Path of Vertex 4 with vertex 5 Values of t Hamiltonian Path t = 4, (n ≥ 11) 4, 1, 3, 7, P [6, 7, n], 6, 2, 5. t = 5, (n ≥ 11) 4, 2, 7, P [6, 7, n], 6, 1, 3, 5. t = 6, (n ≥ 14) 4, 2, 8, 6, 9, P [9, 10, n], 10, 7, 1, 3, 5. t = 7, (n ≥ 15) 4, 7, 10, P [10, 11, n], 11, 8, 1, 3, 6, 9, 2, 5. t = 8, (n ≥ 15) 4, 2, 10, P [10, 11, n], 11, 8, 6, 3, 1, 9, 7, 5. t = 9, (n ≥ 17) 4, 1, 3, 12, P [12, 13, n], 13, 10, P [10, 11, 6], 11, 2, 5. 10 ≤ t ≤ n − 7 (n ≥ 17) 4, 2, t + 2, P [t + 2, t + 3, n], t + 3, t, P [t, t + 1, 6], t +1, 1, 3, 5. The Hamiltonian path of vertex 5 with vertex 6 in Toeplitz graph 2,3, tnT for all values of 4 ≤ t ≤ n − 7 and n ≥ 14 is given in Table 10. Table 10: Hamiltonian Path of Vertex 5 with vertex 6 Conditions on t Hamiltonian Path t = 4, (n ≥ 11) 5, 2, 4, 1, 3, 7, P [6, 7, n], 6. t = 5, (n ≥ 11) 5, 3, 1, 4, 2, 7, P [6, 7, n], 6. t = 6, (n ≥ 12) 5, 3, 1, 7, P [7, 8, n], 8, 2, 4, 6. t = 7, (n ≥ 15) 5, 3, 1, 8, 11, P [10, 11, n], 10, 7, 9, 2, 4, 6. t = 8, (n ≥ 16) 5, 8, 11, P [11, 12, n], 12, 9, 7, 10, 2, 4, 1, 3, 6. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 33, No 1, pp 255-268 265 9 ≤ t ≤ n − 7, (n ≥ 16) 5, 3, 1, 4, 2, t + 2, P [t + 2, t + 3, n], t + 3, P l[6, t + 3, t + 2], 6. The Hamiltonian path of vertex 5 with vertex x such that 7 ≤ x ≤ n and 3x n  in Toeplitz graph 2,3,nT t for 4 ≤ t ≤ n − 7 and n ≥ 25 is “5, 2, 4, 1, 3, 6,  6 6,xH n ,, x ” Main Result Theorem 3.1. The Toeplitz graph 2,3, tnT is Hamiltonian connected for all n ≥ 28 and 8 4 2 n t    Proof. For every  , 2,3, tnx y V T , and 6 5x y n    the Hamiltonian path for different conditions on ,y x for 4 7t n   and for 17n  is shown in Table 11. Table 11: Hamiltonian Path between x and y when 6 5x y n    Conditions on x and y Hamiltonian Path y − x ≥ 5 and n ≥ 16 x, P [x − 1, x, 1], x − 1, P [x − 1, y + 1], y + 1, P [y, y +1, n], y. y − x = 1 and n ≥ 12 x, P [x − 1, x, 1], x − 1, y + 1, P [y, y + 1, n], y. y − x = 2 and n ≥ 13 x, P [x − 1, x, 1], x − 1, x + 1, y + 1, P [y, y + 1, n], y. y − x = 3 and n ≥ 14 x, P [x, x + 1, 1], x + 1, y + 1, x + 2, y + 2, P [y + 2, y +3, n], y + 3, y. y − x = 4 and n ≥ 16 x, P [x − 1, x, 1], x − 1, x + 2, y + 1, P [y + 1, y + 2, n], y +2, x + 3, x + 1, y. The Hamiltonian path of vertex 4 with vertex 6 in Toeplitz graph 2,3,nT t for all values of 4 ≤ t ≤ n − 7 is given in Table 12. Table 12: Hamiltonian Path of Vertex 4 with vertex 6 Values of t Hamiltonian Path t = 4, (n ≥ 12) 4, 1, 3, 7, P [7, 8, n], 8, 5, 2, 6. t = 5, (n ≥ 11) 4, 1, 3, 5, 2, 7, P [6, 7, n], 6. t = 6, (n ≥ 11) 4, 2, 5, 3, 1, 7, P [6, 7, n], 6. t = 7, (n ≥ 12) 4, 2, 5, 7, P [7, 8, n], 8, 1, 3, 6. t = 8, (n ≥ 16) 4, 2, 5, 7,  9 7 7,H n , 9, 1, 3, 6. 9 ≤ t ≤ n – 7, (n ≥ 16) 4, 1, 3, 5, 2, t+2, P [t+2, t+3, n], t+3, 'P [6, t+3, t+2], 6. The Hamiltonian path of vertex 4 with vertex 7 in Toeplitz graph 2,3,nT t for all values of 4 ≤ t ≤ n − 7 is given in Table 13. The Hamiltonian path of vertex 4 with vertex 8 in Toeplitz graph 2,3,nT t for all values of 4 ≤ t ≤ n − 7 is given in Table 14. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 33, No 1, pp 255-268 266 The Hamiltonian path of vertex 4 with vertex 9 in Toeplitz graph 2,3,nT t for all values of 4 7t n   is given in Table 15. Table 13: Hamiltonian Path of Vertex 4 with vertex 7 Values of t Hamiltonian Path t = 4, (n ≥ 11) 4, 1, 3, 5, 2, 6, P [6, 7, n], 7. t = 5, (n ≥ 11) 4, 2, 5, 3, 1, 6, P [6, 7, n], 7. t = 6, (n ≥ 14) 4, 1, 3, 5, 2, 8, 6, 9, P [9, 10, n], 10, 7. t = 7, (n ≥ 14) 4, 2, 5, 3, 1, 8, 6, 9, P [9, 10, n], 10, 7. t = 0 (mod 2) 8 ≤ t ≤ n − 7 (n ≥ 5) 4, 2, t+2, P [t +2, t+3, n], t+ 3, t, 2t  , . . . , 8, 6, 9, 11, . . . , t + 1, 1, 3, 5, 7. t = 1 (mod 2) 9 ≤ t ≤ n − 7 (n ≥ 17) 4, 2, t+2, P [t+2, t+3, n], t+3, t, 2t  , t−4, . . . , 9, 6, 8, 10, . . . , t + 1, 1, 3, 5, 7. Table 14: Hamiltonian Path of Vertex 4 with vertex 8 Values of t Hamiltonian Path t = 4, (n ≥ 15) 4, 1, 3, 5, 2, 6, 9, 7, 10, P [10, 11, n], 11, 8. t = 5, (n ≥ 15) 4, 2, 5, 3, 1, 6, 9, 7, 10, P [10, 11, n], 11, 8. t = 6, (n ≥ 15) 4, 2, 5, 3, 1, 7, 10, P [9, 10, n], 9, 6, 8. t = 7, (n ≥ 18) 4, 1, 3, 5, 2, 9,  8 9 6,H n , 8. t = 8, (n ≥ 14) 4, 7, 5, 2, 10, P [9, 10, n], 9, 1, 3, 6, 8. t = 1 (mod 2) 4, 1, t + 1, t − 1, t − 3, . . . , 10, 7, 9, 11, . . . , t, t + 3, P [t + 2, t +3, n], t + 2, 2, 5, 3, 6,8 9 ≤ t ≤ n – 7, (n ≥ 16) t = 0 (mod 2) 4, 1, t + 1, t − 1, t − 3, . . . , 7, 10, 12, . . . , t, t + 3, P [t + 2, t +3, n], t + 2, 2, 5, 3, 6, 8. 10 ≤ t ≤ n – 7 , (n ≥ 17) Table 15: Hamiltonian Path of Vertex 4 with vertex 9 Values of t Hamiltonian Path t = 4, (n ≥ 15) 4, 1, 3, 5, 2, 6,  9 6 6,H n , 9. 6 t = 5, (n ≥ 15) 4, 1, 3, 5, 2, 7,  9 7 6,H n , 9. 7 t = 6 (n ≥ 19) 4, 1, 3, 5, 2, 8,  9 8 6,H n ], 9. 8 7,t  ( 19n  ) 4, 2, 5, 3, 1, 8,  9 8 6,H n , 9. t = 8, (n ≥ 15) 4, 1, 3, 6, 8, 11, P [10, 11, n], 10, 2, 5, 7, 9. t = 9, (n ≥ 15) 4, 1, 3, 6, 8, 10, P [10, 11, n], 11, 2, 5, 7, 9. t = 1 (mod 2) 11 ≤ t ≤ n − 7 (n ≥ 18) 4, 7, 5, 2, t+2, P [t+2, t+3, n], t+3, t, t−2, t−4, . . . , 11, 8, 10, 12, . . . , t + 1, 1, 3, 6, 9. t = 0 (mod 2) 10 ≤ t ≤ n − 7 (n ≥ 17) 4, 7, 5, 2, t+2, P [t+2, t+3, n], t+3, t, t−2, t−4, . . . , 8, 11, 13, 15, . . . , t + 1, 1, 3, 6, 9. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 33, No 1, pp 255-268 267 The Hamiltonian path of vertex 4 with vertex 10 in Toeplitz graph 2,3,nT t for all values of 4 7t n   is given in Table 16. Table 16: Hamiltonian Path of Vertex 4 with vertex 10 Condition on t Hamiltonian Path 4 ≤ t ≤ n − 7, 8t  , (n ≥ 22) 4, 1, 3, 5, 2, t + 2,  2 10 6,tH n , 10. 10 t = 8, (n ≥ 20) 4, 2, 5, 3, 1, 9,  10 9 6,H n , 10. 9 The Hamiltonian path of vertex 4 with vertex x for 11 5x n   in Toeplitz graph 2,3,nT t for all values of 8 4 2 n t    and 27n  is given in Table 17. Table 17: Hamiltonian Path of Vertex 4 with vertex 11 5x n   Condition on t Hamiltonian Path t = 4, (n ≥ 24) 4, 1, 3, 5, 2, 6,  6 6,xH n , x. For all 7 ≤ x ≤ n. 6 t = 5, (n ≥ 24) 4, 2, 5, 3, 1, 6,  6 6,xH n , x. For all 7 ≤ x ≤ n. 6 t = 6, (n ≥ 24) 4, 2, 5, 3, 1, 7,  7 6,xH n , x. For all 8 ≤ x ≤ n. 7 t = 7, (n ≥ 25) 4, 2, 5, 3, 1, 8,  8 6,xH n , x. For all 9 ≤ x ≤ n. 8 t = 8, (n ≥ 26) 4, 1, 3, 5, 2, 10,  10 6,xH n , x. For all 11 ≤ x ≤ n. 10 9,t   26n  4, 2, 5, 3, 1, 10,  10 6,xH n , x. For all 11 ≤ x ≤ n. 10 ≤ t ≤ n − 7, x = t+1, (n ≥ 21) 4, 1, 3, 5, 2, t + 2,  2 6,x th n , x. For all 11 ≤ x ≤ n − 5. 10 ≤ t ≤ n − 7,x /= t+1, (n ≥ 21) 4, 2, 5, 3, 1, t+1,  1 6,t xh n , x Hamiltonian path of Table 11, x. The Hamiltonian path of vertex 4 with vertex 3n  , for 8 10 2 n t    and for 28n  is “ 4,1,3,5,2, 2,t       2, 1,6 , 1, ' 1, 1, 2 , 1, 1, , 5 , , , 2, 4, 1, 3P t t t P t n t t n t P n t n t n n t n n n n n                  ’’. 2. Conclusion S. Malik and T. Zamfirescu investigated Hamiltonian properties of Toeplitz graphs in [8]. M. F. Nadeem Ayesha Shabbir and Tudor Zamfirescu complete the picture of Toeplitz graphs 1 2, , 1,3,n nT t t T t and 1,5, tnT in [9]. In this paper we proved that the Toeplitz graphs 2,3, tnT are Hamiltonian connected for 28n  and 8 4 2 n t    . It would be interesting to derive similar results for other families of Toeplitz graphs such as 2,5, tnT and generalize the results for 2,s, tnT . American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2017) Volume 33, No 1, pp 255-268 268 References [1] R. Van Dal, G. Tijssen, Z. Tuza, J. A. A. Van Der Veen, Zamfirexcu, T. Zamfirescu, “Hamiltonian properties of Toeplitz graphs”, Discrete Mathe- matics 159, 69–81 (1996). [2] R. Euler, “ Characterizing bipartite Toeplitz graphs”. Theor. Comput. Sci. 263, 47–58 (2001). [3] R. Euler, H. Leverge, T. Zamfirescu, “A characterization of infinite, bipartite Toeplitz graphs”. In: Tung- Hsin, K. (ed.) Combinatorics and Graph Theory 95, Vol. 1. Academia Sinica, pp. 119–130. World Scientific, Sin- gapore (1995). [4] R. Euler, T. Zamfirescu, “ On planar Toeplitz graphs”. Graphs Comb. 29, 13111327 (2013). [5] C. Heuberger, “On Hamiltonian Toeplitz graphs”. Discret. Math. 245, 107– 125 (2002). [6] S. Malik, “Hamiltonicity in directed Toeplitz graphs of maximum (out or in) degree 4”. Util. Math. 89, 33–68 (2012) [7] S. Malik, A. M. Qureshi, “Hamiltonian cycles in directed Toeplitz graphs”. Ars Comb. 109, 511– 526 (2013). [8] S. Malik, T. Zamfirescu, “ Hamiltonian connectedness in directed Toeplitz graphs”. Bull. Math. Soc. Sci. Math. Roum. 53 (101) No. 2, 145156 (2010). [9] M. F. Nadeem, A. Shabbir, T. Zamfirescu, “Hamiltonian Connectedness of Toeplitz Graphs”. Springer Basel 2015 P. Cartier et al. (eds.), Mathematics in the 21st Century, Springer Proceedings in Mathematics & Statistics 98, DOI 10.1007/978-3-0348-0859-08.