id	author	title	date	pages	extension	mime	words	sentence	flesch	summary	cache	txt
ejpam-546	Alsina, Claudio; Nelsen, Roger B.	An Invitation to Proofs Without Words	2009	10	.pdf	application/pdf	3074	234	77	We begin with some theorems and proofs about the simplest figurate numbers: triangular numbers and squares. Sums of powers of 9 are triangular numbers, i.e., for all n≥ 0, 1+ 9+ 92 + . .	cache/ejpam-546.pdf	txt/ejpam-546.txt