Talk:Squared triangular number

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It would be nice to include the picture proof from http://users.tru.eastlink.ca/~brsears/math/oldprob.htm#s32, since it is clearer than the one already on this page, but I am not sure about the copyright status of the images. Please advise.

Loeb 02:17, 30 October 2007 (UTC)[reply]

It is a pretty proof. I think only the second of the two images there can easily stand on its own. BUT, I would like to know the source of the proof. Has it been published anywhere? Is it the same as one of the existing proofs already known in the article? I don't think a web page makes an adequate reference for a problem with as much history as this one. —David Eppstein 02:22, 30 October 2007 (UTC)[reply]

Proof

Who was the first to prove this theorem? I've seen it called Nicomachus' Theorem, but did he prove it or merely observe it? If not, did Āryabhaṭa? Al-Karajī?

CRGreathouse (t | c) 18:22, 31 August 2009 (UTC)[reply]