EUROPEAN JOURNAL OF PURE AND APPLIED MATHEMATICS Vol. 12, No. 2, 2019, 279-293 ISSN 1307-5543 – www.ejpam.com Published by New York Business Global Hankel Transform of (q, r)-Dowling Numbers Roberto B. Corcino1, Mary Joy R. Latayada2,∗, Mary Ann Ritzell P. Vega3 1 Research Institute for Computational Mathematics and Physics, Cebu Normal University, 6000 Cebu City, Philippines 2 Department of Mathematics, Caraga State University, 8600 Butuan City, Philippines 3 Department of Mathematics and Statistics, College of Science and Mathematics, Mindanao State University-Iligan Institute of Technology, 9200 Iligan City, Philippines Abstract. In this paper, the authors establish certain combinatorial interpretation for q-analogue of r-Whitney numbers of the second kind defined by Corcino and Cañete in the context of A- tableaux. They derive convolution-type identities by making use of the combinatorics of A- tableaux. Finally, they define a q-analogue of r-Dowling numbers and obtain some necessary properties including its Hankel transform. Key Words and Phrases: Whitney numbers, Dowling numbers, generating function, q-analogue, q-exponential function, A-tableau, convolution formula, Hankel transform, Hankel matrix, binomial transform. 1. Introduction The binomial transform B of a sequence A = {an} is the sequence {bn} defined by bn = n∑ k=0 (−1)k ( n k ) ak. That is, B(A) = bn. It is one of the common and useful transforms that frequently appeared in the literature of integer sequences (see [16]). The inverse binomial transform (or inverse transform) C of a sequence A is the sequence {cn} defined by cn = n∑ k=0 ( n k ) ak. That is, C(A) = cn. ∗Corresponding author. DOI: https://doi.org/10.29020/nybg.ejpam.v12i2.3406 Email addresses: rcorcino@yahoo.com (R. Corcino), mrlatayada@gmail.com (MJ. Latayada), maryannritzel.vega@g.msuiit.edu.ph (MAR. Vega) http://www.ejpam.com 279 c© 2019 EJPAM All rights reserved. R. Corcino, MJ. Latayada, MAR. Vega / Eur. J. Pure Appl. Math, 12 (2) (2019), 279-293 280 The Hankel matrix Hn of order n of a sequence A = {a0, a1, . . . , an} is given by Hn = (ai+j)0≤i,j≤n. The Hankel determinant hn of order of n of A is the determinant of the corresponding Hankel matrix of order n. That is, hn = det(Hn). The Hankel transform of the sequence A, denoted by H(A), is the sequence {hn} of Hankel determinants of A. For instance, the Hankel transform of the sequence of Catalan numbers C = { 1 n+1 ( 2n n ) }∞n=1, is given by H(C) = {1, 1, 1, . . . , } and the sequence of the sum of two consecutive Catalan numbers, an = cn + cn+1, with cn the nth Catalan numbers, has the Hankel transform H(an) = {F2n+1}∞n=0 where Fn is the nth Fibonacci numbers [12]. One remarkable property of Hankel transform is established by Layman [12], which states that the Hankel transform of an integer sequence is invariant under binomial and inverse transforms. That is, if A is an integer sequence, B is binomial transform of A and C is the inverse transform of A, then H(B(A)) = H(A) and H(C(A)) = H(A). This property played an important role in proving that the Hankel transform of the se- quence of Bell number {Bn)} [1] and that of r-Bell numbers {Bn,r} [14] are equal. Recently, in the paper by R. Corcino and C. Corcino [7], this property has also been used in proving that the Hankel transform of the sequence of generalized Bell numbers {Gn,r,β} is given by H(Gn,r,β) = n∏ j=0 βjj! where Gn,r,β is the sum of (r, β)-Stirling numbers { n k } r,β Gn,r,β = n∑ k=0 { n k } r,β (see [5, 8]), which are also known as (r, β)-Bell numbers. In the same paper, the authors have made an attempt to establish the Hankel transform for the q-analogue of (r, β)-Bell numbers. However, they are not successful with their attempt and have conjectured that the Hankel transform for the q-analogue of (r, β)-Bell numbers when r = 0 is equal to H ( Gqn,β,0 ) = n∏ k=0 qf(n,k)[β]kq [k]qβ ! (1) for some number f(n, k), which is a function of n and k. With this, the present au- thors have decided to use other method. Recently, R. Corcino et al.[9] have successfully R. Corcino, MJ. Latayada, MAR. Vega / Eur. J. Pure Appl. Math, 12 (2) (2019), 279-293 281 established the Hankel transform for the q-analogue of noncentral Bell numbers. This motivates the present authors to use this method to establish the Hankel transform for the q-analogue of (r, β)-Bell numbers Gn,r,β. It is important to note that the numbers Gn,r,β are equivalent to the r-Dowling numbers Dm,r(n), which are defined as the sum of r-Whitney numbers of the second kind, denoted by Wm,r(n, k). That is, Dm,r(n) = n∑ k=0 Wm,r(n, k). The term “r-Dowling numbers” was introduced by Cheon and Jung [3]. 2. A q-Analogue of Wm,r(n, k): Second Form A q-analogue of both kinds of Stirling numbers was first defined by Carlitz in [2]. The second kind of which, known as q-Stirling numbers of the second kind, is defined in terms of the following recurrence relation Sq[n, k] = Sq[n− 1, k − 1] + [k]qSq[n− 1, k] (2) in connection with a problem in abelian groups, such that when q → 1, this gives the triangular recurrence relation for the classical Stirling numbers of the second kind S(n, k) S(n, k) = S(n− 1, k − 1) + kS(n− 1, k). (3) A different way of defining q-analogue of Stirling numbers of the second kind has been adapted in the paper by [10] which is given as follows Sq[n, k] = qk−1Sq[n− 1, k − 1] + [k]qSq[n− 1, k]. (4) This type of q-analogue gives the Hankel transform of q-exponential polynomials and numbers which are certain q-analogue of Bell polynomials and numbers. Recently, a q- analogue of r-Whitney numbers of the second kind was defined by Corcino and Cañete [6] parallel to the definition for q-analogue of noncentral Stirling numbers of the second kind as follows: Definition 1. For non-negative integers n and k, and real number a, a q-analogue Wm,r[n, k]q of Wm,r(n, k) is defined by Wm,r[n, k]q = qm(k−1)+rWm,r[n− 1, k − 1]q + [mk + r]qWm,r[n− 1, k]q. (5) where Wm,r[0, 0]q = 1, Wm,r[n, k]q = 0 for n < k or n, k < 0 and [t− k]q = 1 qk ([t]q − [k]q). Remark 1. When m = 1 and r = 0, the relation (5) reduces to (4). This implies that W1,0[n, k]q = Sq[n, k]. (6) R. Corcino, MJ. Latayada, MAR. Vega / Eur. J. Pure Appl. Math, 12 (2) (2019), 279-293 282 The q-analogue Wm,r[n, k]q satisfies the following properties: Vertical and Horizontal Recurrence Relations Wm,r[n+ 1, k + 1]q = qmk+r n∑ j=k [m(k + 1) + r]n−jq Wm,r[j, k]q; (7) Wm,r[n, k]q = n−k∑ j=0 (−1)jq−r−m(k+j) rk+j+1,q rk+1,q Wm,r[n+ 1, k + j + 1]q; (8) Horizontal Generating Function n∑ k=0 Wm,r[n, k]q[t− r|m]k,q = [t]nq . (9) Explicit Formula Wm,r[n, k]q = 1 [k]qm ![m]kq k∑ j=0 (−1)k−jqm(k−j2 ) [ k j ] qm [jm+ r]nq (10) = 1 [k]qm ![m]kq [ ∆k qm,m[x+ r]nq ] x=0 (11) Exponential Generating Function ∑ n≥0 Wm,r[n, k]q [t]nq [n]q! = 1 [k]qm![m]kq [ ∆qm,mkeq ( [x+ jm+ r]q[t]q )] x=0 . (12) Rational Generating Function Ψk(t) = ∑ n≥k Wm,r[n, k]q[t] n q = qm(k2)+kr[t]kq∏k j=0(1− [mj + r]q[t]q) . Explicit Formula in Symmetric Function Form Wm,r[n, k]q = qm(k2)+kr ∑ S1+S2+···Sk=n−k k∏ j=0 [mj + r] Sj q = ∑ 0≤j1≤j2≤···jn−k≤k qm(k2)+kr n−k∏ i=1 [mj + r]q. R. Corcino, MJ. Latayada, MAR. Vega / Eur. J. Pure Appl. Math, 12 (2) (2019), 279-293 283 We now define another form of q-analogue of r-Whitney numbers of the second, denoted by W ∗m,r[n, k]q, as follows W ∗m,r[n, k]q := q−kr−m(k2)Wm,r[n, k]q. Hence, W ∗m,r[n, k] = ∑ 0≤j1≤j2≤...≤jn−k≤k n−k∏ i=1 [mji + r]q. (13) All other properties parallel to those of Wm,r[n, k]q can easily be established by imbed- ding the factor q−kr−m(k2) in the derivations or multiply directly to the resulting identi- ties/formula. Definition 2. [13] An A-tableau is a list φ of column c of a Ferrer’s diagram of a partition λ(by decreasing order of length) such that the lengths |c| are part of the sequence A = (ri)i≥0, a strictly increasing sequence of nonnegative integers. Let ω be a function from the set of nonnegative integers N to a ring K. Suppose Φ is an A-tableau with l columns of lengths |c| ≤ h. We use TAr (h, l) to denote the set of such A-tableaux. Then, we set ωA(Φ) = ∏ c∈Φ ω(|c|). Note that Φ might contain a finite number of columns whose lengths are zero since 0 ∈ A = {0, 1, 2, . . . , k} and if ω(0) 6= 0. From this point onward, whenever an A-tableau is mentioned, it is always associated with the sequence A = {0, 1, 2, . . . , k}. We are now ready to mention the following theorem. Theorem 1. Let ω : N → K denote a function from N to a ring K (column weights according to length) which is defined by ω(|c|) = [m|c|+ r]q where r is a complex number, and |c| is the length of column l of an A-tableau in TAr (k, n− k). Then W ∗m,r[n, k] = ∑ φ∈TAr (k,n−k) ∏ c∈φ ω(|c|). Proof. Let Φ ∈ TAr (k, n − k). This means that Φ has exactly n − k columns say c1, c2, · · · , cn−k whose lengths are j1, j2, · · · , jn−k, respectively. Now, for each column ci ∈ Φ, i = 1, 2, 3, · · · , n− k, we have |ci| = ji and ω(|ci|) = [m|ji|+ r]q. R. Corcino, MJ. Latayada, MAR. Vega / Eur. J. Pure Appl. Math, 12 (2) (2019), 279-293 284 Then ∏ c∈Φ ω(|c|) = n−k∏ i=1 ω(|ci|) = n−k∏ i=1 [m|ji|+ r]q. Since Φ ∈ TAr (k, n− k), then∑ Φ∈TAr (k,n−k) ∏ c∈Φ ω(|c|) = ∑ 0≤j1≤j2≤...≤jn−k≤k ∏ c∈Φ ω(|c|) = ∑ 0≤j1≤j2≤...≤jn−k≤k n−k∏ i=1 [m|ji|+ r]q = W ∗m,r[n, k]. � Suppose that for some numbers r1 and r2, we have r = r1 + r2. Then, equation (13) yields W ∗m,r[n, k]q = ∑ 0≤j1≤j2≤...≤jn−k≤k n−k∏ i=1 [(mji + r1) + r2]q. That is, for any φ ∈ TAr (k, n− k), ωA(φ) = ∏ c∈φ [(mji + r1) + r2]q, where |c| ∈ {0, 1, 2, . . . , k}. Note that the weight of each column of φ can be considered as a finite sum with additive constant r2, that is, for each c ∈ φ, we can write ω(|c|) = 1 qr2 (ω∗(|c|) + [r2]q), (14) where ω∗(|c|) = [m|c|+ r1]q. The following theorem determines how an additive constant affects the recurrence formula for Wm,r[n, k]q. From Theorem 1, W ∗m,r[n, k]q = ∑ φ∈TAr (k,n−k) ωA(φ) = ∑ φ∈TAr (k,n−k) ∏ c∈φ ω(|c|) where ωA(φ) = ∏ c∈φ [m|c|+ r]q, where |c| ∈ {0, 1, . . . , k} = n−k∏ i=1 [mji + r]q, where ji ∈ {0, 1, . . . , k}. R. Corcino, MJ. Latayada, MAR. Vega / Eur. J. Pure Appl. Math, 12 (2) (2019), 279-293 285 If r = r1 + r2 for some r1 and r2, then by (14), ωA(φ) = n−k∏ i=1 1 qr2 (ω∗(ji) + [r2]q) , where ω∗(ji) = [mji + r1]q = q−(n−k)r2 (ω∗(j1) + [r2]q) (ω∗(j2) + [r2]q) · · · (ω∗(jn−k) + [r2]q)) = q−(n−k)r2 n−k∑ l=0 ([r2]q) n−k−l ∑ j1≤j1≤j2≤...≤jl≤jn−k l∏ i=1 ω∗(ji). Suppose Bφ is the set of all A-tableaux corresponding to φ such that for each ψ ∈ Bφ, either ψ has no column whose weight is [r2]q, or ψ has one column whose weight is [r2]q, or ψ has two columns whose weights are [r2]q, or ... ψ has (n− k) columns whose weights are [r2]q. Then, we may write ωA(φ) = ∑ ψ∈Bφ ωA(ψ). Now, if l columns in ψ have weights other than [r2]q, then ωA(ψ) = ∏ c∈ψ ω∗(|c|) = q−(n−k)r2([r2]q) n−k−r r∏ i=1 ω∗(qi) where q1, q2, . . . , qr ∈ {j1, j2, . . . , jn−k}. Note that for each l, there corresponds( n− k l ) tableaux with l columns having weights ω∗(ji) = [mji+r1]q. It can be easily verified that, |TAr (k, n− k)| = ( (n− k) + k n− k ) = ( n n− k ) = ( n k ) . Thus, ∀φ ∈ TAr (k, n− k), Bφ contains a total of( n k )( n− k l ) R. Corcino, MJ. Latayada, MAR. Vega / Eur. J. Pure Appl. Math, 12 (2) (2019), 279-293 286 tableaux with l columns of weights ω∗(ji). However, only ( l+k l ) tableaux with l columns in Bφ are distinct. Hence, every distinct tableaux ψ with l columns of weights other than [r2]q appears ( n k )( n−k l )( l+k l ) = ( n l + k ) times in the collection. Thus, ∑ φ∈TAr (k,n−k) ωA(φ) = n−k∑ l=0 ( n l + k ) q−(n−k)r2([r2]q) n−k−l ∑ ϕ∈B̄l ∏ c∈ϕ ω∗(|c|) where B̄l denotes the set of all tableaux ϕ having l columns of weights ω∗(ji) = [mji+r1]q. Reindexing the double sum, we get ∑ φ∈TAr (k,n−k) ωA(φ) = n∑ j=k ( n j ) q−nr2([r2]q) n−j ∑ ϕ∈B̄j−k ∏ c∈ϕ ω∗(|c|) where B̄j−k is the set of all tableaux ϕ with j − k columns of weights ω∗(ji) = [mji + r1]q for each i = 1, 2, . . . , j − k. Clearly B̄j−k = TAr1(k, j − k). Hence, ∑ φ∈TAr (k,n−k) ωA(φ) = n∑ j=k ( n j ) q−nr2([r2]q) n−j ∑ ϕ∈TAr1 (k,j−k) ωA(ϕ). Applying Theorem 1, we obtain the following theorem. Theorem 2. The q-analogue W ∗m,r[n, k]q satisfies the following identity W ∗m,r[n, k]q = n∑ j=k (−1)n−j ( n j ) q−nr2 [r2]n−jq W ∗m,r1 [j, k]q where r = r1 + r2 for some numbers r1 and r2. Suppose φ1 is a tableau with k − s columns whose lengths are in the set {0, 1, . . . , s}, and φ2 be a tableau with n− k − j columns whose lengths are in the set {s+ 1, s+ 2, . . . , s+ j + 1} Then φ1 ∈ TA1(s, k − s) and φ2 ∈ TA2(j, n− k − j) R. Corcino, MJ. Latayada, MAR. Vega / Eur. J. Pure Appl. Math, 12 (2) (2019), 279-293 287 where A1 = {0, 1, . . . , s} and A2 = {s+ 1, s+ 2, . . . , s+ j + 1}. Notice that by joining the columns of φ1 and φ2, we obtain an A-tableau φ with n− s− j columns whose lengths are in the set A = A1 ∪A2 = {0, 1, . . . , s+ j+ 1}. That is, φ ∈ TA(s+ j+ 1, n− s− j). Then, ∑ φ∈TA(s+j+1,n−s−j) ωA(φ) = n−j∑ k=s  ∑ φ1∈TA1 (s, k−s) ωA1(φ1)   ∑ φ2∈TA2 (j, n−k−j) ωA2(φ2)  . Note that ∑ φ2∈TA2 (j, n−k−j) ωA2(φ2) = ∑ φ2∈TA2 (j, n−k−j) ∏ c∈φ2 [m|c|+ r]q = ∑ s+1≤g1≤...≤g n−k−j≤ s+j+1 n−k−j∏ i=1 [mgi + r]q = ∑ 0≤g1≤...≤g n−k−j≤j n−k−j∏ i=1 [mgi +m(s+ 1) + r]q. Thus, ∑ 0≤g1≤...≤gn−s−j≤s+j+1 n−s−j∏ i=1 [mgi + r]q = n−j∑ k=s  ∑ 0≤g1≤...≤gk−s≤s k−s∏ i=1 [mgi + r]q   ∑ 0≤g1≤...≤gn−k−j≤j n−k−j∏ i=1 [mgi +m(s+ 1) + r]q . By (13), we obtain the following theorem. Theorem 3. The q-analogue W ∗m,r[n, k] satisfies the following convolution-type identity W ∗m,r[n+ 1, s+ j + 1]q = n∑ k=0 W ∗m,r[k, s]qW ∗ m,r+m(s+1)[n− k, j]q. The next theorem provides another form of convolution-type identity. Theorem 4. The q-analogue W ∗m,r[n, k]q satisfies the following second form of convolution formula W ∗m,r[s+ j, n]q = n−j∑ k=s W ∗m,r[s, k]qW ∗ m,r+mk[j, n− k]q. R. Corcino, MJ. Latayada, MAR. Vega / Eur. J. Pure Appl. Math, 12 (2) (2019), 279-293 288 Proof. Let φ1 be a tableau with s− k columns whose lengths are in A1 = {0, 1, . . . , k}, and φ2 be a tableau with j − n+ k columns whose lengths are in A2 = {k, k + 1, . . . , n}. Then φ1 ∈ TA1(k, s− k) and φ2 ∈ TA2(n− k, j−n+ k). Using the same argument above, we can easily obtain the convolution formula. � 3. (q, r)−Dowling Number and Its Hankel Transform In this section, we define a q-analogue of the r-Dowling numbers and obtain some combinatorial properties that will be used to establish its Hankel transform. A q-analogue of the r-Dowling numbers, denoted by D̃m,r[n]q, is defined by D̃m,r[n]q = n∑ k=0 W̃m,r[n, k]q where W̃m,r[n, k]q = qkrW ∗m,r[n, k]q = q−m(k2)Wm,r[n, k]. For brevity, we use the term (q, r)-Dowling numbers for D̃m,r[n]q. Remark 2. When m = 1 and r = 0, (6) yields W̃1,0[n, k]q = q−(k2)W1,0[n, k] = q−(k2)Sq[n, k] = S̃q[n, k]. (15) It follows that the (q, r)-Dowling numbers reduces to D̃1,0[n]q = ẽq,n[1] (16) where ẽq,n[z] is the q-exponential polynomial in [11] defined by ẽq,n[z] = n∑ k=0 S̃q[n, k]zk. (17) Remark 3. We recall that the Hankel transform of the q-exponential polynomial ẽq,n[z] is given by H (ẽq,n(z)) = q( n+1 3 )[0]![1]! . . . [n]!(z)( n+1 2 ). It can easily be verified that the Hankel transform of ēq,n[z] = n∑ k=0 S̃q[n, k]zn−k (18) is equal to that of ẽq,n[z]. R. Corcino, MJ. Latayada, MAR. Vega / Eur. J. Pure Appl. Math, 12 (2) (2019), 279-293 289 Remark 4. Since Wm,0[n, k]q = [m]n−kq  1 [k]qm ! k∑ j=0 (−1)k−jqm(k−j2 ) [ k j ] qm [j]nqm  = [m]n−kq Sqm [n, k], we have W̃m,0[n, k]q = q−m(k2)Wm,0[n, k] = [m]n−kq (qm)−(k2) Sqm [n, k] = [m]n−kq S̃qm [n, k]. This implies that D̃m,0[n]q = n∑ k=0 W̃m,0[n, k]q = n∑ k=0 S̃qm [n, k][m]n−kq . (19) Thus, using Remark 3, the Hankel transform of D̃m,0[n]q is given by H ( D̃m,0[n]q) ) = H (ēqm,n([m]q)) = qm(n+1 3 )[0]qm ![1]qm ! . . . [n]qm ![m] (n+1 2 ) q (20) Clearly, when q → 1, D̃m,r[n]q → D̃m,r(n), the r-Dowling numbers. By making use of Theorem 2, with r1 = r − 1 and r2 = 1 and multiplying both sides by q−kr,we have W̃m,r[n, k]q = n∑ j=k (−1)n−j ( n j ) q−nW̃m,r−1[j, k]q. (21) Summing up both sides of (21), we have D̃m,r[n]q = n∑ k=0 n∑ j=k (−1)n−j ( n j ) q−nW̃m,r−1[j, k]q = n∑ j=0 j∑ k=0 (−1)n−j ( n j ) q−nW̃m,r−1[j, k]q = n∑ j=0 (−1)n−j ( n j ) q−n j∑ k=0 W̃m,r−1[j, k]q = n∑ j=0 (−1)n−j ( n j ) q−nD̃m,r−1[j]q. The following theorem states formally the above recurrence relation for D̃m,r[n]q. Theorem 5. The (q, r)-Dowling numbers satisfy the following relation qnD̃m,r[n]q = n∑ j=0 (−1)n−j ( n j ) D̃m,r−1[j]q. (22) R. Corcino, MJ. Latayada, MAR. Vega / Eur. J. Pure Appl. Math, 12 (2) (2019), 279-293 290 The following corollary is a direct consequence of Theorem 5 which can be proved using the inversion formula by Riordan [4, 15]. Corollary 1. The (q, r)-Dowling numbers satisfy the following relations D̃m,r−1[n]q = n∑ j=0 ( n j ) qjD̃m,r[j]q. (23) To establish the Hankel transform of D̃m,r[n]q, we need the concept of rising k-binomial transform by Spivey and Steil [17] as well as its property in relation to Hankel transform. Definition 3. (Spivey-Steil [17]) The rising k-binomial transform R of a sequence A = {an} is the sequence R(A; k) = {rn}, where rn is given by rn = n∑ j=0 ( n j ) kjaj , k 6= 0. (24) We use R(A, k) to denote the set of rising k-binomial transform of A. That is, R(A, k) = {rn}. Then we have the following theorem by Spivey and Steil. Theorem 6. (Spivey-Steil [17]) Given a sequence A = {a0, a1, . . . , }. Let H(A) = {hn}. Then H(R(A, k)) = {a0, 0, 0, . . . , }. If k 6= 0, H(R(A, k)) = {kn(n+1)hn}. Now, we are ready to state the main result of the paper. Theorem 7. The Hankel transform of the sequence of (q, r)-Dowling numbers {D̃m,r[n]q} is given by H(D̃m,r[n]q) = qm(n+1 3 )−rn(n+1)[0]qm ![1]qm ! . . . [n]qm ![m] (n+1 2 ) q . (25) Proof. Using equation (18) in Remark 4, we have H(D̃m,0[n]q) = qm(n+1 3 )[0]qm ![1]qm ! . . . [n]qm ![m] (n+1 2 ) q . (26) From Corollary 1, we say that D̃m,r−1[n]q is the binomial transform of qnD̃m,r[n]q. This means that B(qnD̃m,r[n]q) = D̃m,r−1[n]q. Hence, by Layman’s Theorem [12], H(B(qnD̃m,r[n]q)) = H(qnD̃m,r[n]q). R. Corcino, MJ. Latayada, MAR. Vega / Eur. J. Pure Appl. Math, 12 (2) (2019), 279-293 291 That is, H(D̃m,r−1[n]q) = H(qnD̃m,r[n]q). Now, Corollary 1 can also be stated as D̃m,r−1[n]q is the rising q-binomial transform of D̃m,r[n]q. Using Spivey-Steil Theorem, with A = {D̃m,r[n]q}, hn = H(D̃m,r[n]q) and rn = D̃m,r−1[n]q, we have H(D̃m,r−1[n]q) = qn(n+1)H(D̃m,r[n]q). We observe that, when r = 1 and using (26), we have H(D̃m,1[n]q) = q−n(n+1)H(D̃m,0[n]q) = q−n(n+1)qm(n+1 3 )[0]qm ![1]qm ! . . . [n]qm ![m] (n+1 2 ) q = qm(n+1 3 )−n(n+1)[0]qm ![1]qm ! . . . [n]qm ![m] (n+1 2 ) q Also, when r = 2, H(D̃m,2[n]q) = qm(n+1 3 )−2n(n+1)[0]qm ![1]qm ! . . . [n]qm ![m] (n+1 2 ) q . Continuing this argument, we obtain H(D̃m,r[n]q) = qm(n+1 3 )−rn(n+1)[0]qm ![1]qm ! . . . [n]qm ![m] (n+1 2 ) q � Remark 5. When m = 1, the Hankel transform in (25) reduces to H(D̃1,r[n]q) = q( n+1 3 )−rn(n+1)[0]![1]! . . . [n]!, which is exactly the Hankel transform for the q-noncentral Bell numbers in [9]. Remark 6. When q → 1, the Hankel transform in (25) yields H(D̃m,r[n]q) = [0]![1]! . . . [n]!m(n+1 2 ), which is exactly the Hankel transform for the q-analogue of (r, β)-Bell numbers in [9]. Remark 7. The Hankel transform in (25) can also be written as H(D̃m,r[n]q) = qm(n+1 3 ) n∏ k=0 q−2rk[m]kq [k]qm ! such that, when r = 0, we have H(D̃m,0[n]q) = qm(n+1 3 ) n∏ k=0 [m]kq [k]qm !, which is exactly the conjectured Hankel transform in (1) with m = β and n∏ k=0 f(n, k) = qm(n+1 3 ). 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