Talk:Triangular number/Comments
Currently one long unstructured section consisting of a sequence of unrelated facts. Needs organization and editing. —David Eppstein 01:44, 24 April 2007 (UTC)
Add Fermat's Theorem on triangular numbers (first proved by Gauss).
I think that a mention of the theorem that every positive integer can be represented as the sum of at most 3 triangular numbers, stated by Fermat and first proved by Gauss in Disquisitiones Arithmeticae, should be added to this page. Perhaps also a reference to its generalization, also stated by Fermat and proved by Cauchy (?) after work by others that every positive integer was a sum of at most 3 triangular numbers, 4 square numbers, 5 pentagonal numbers, etc. Yes I know the history of the 4-square theorem, but I don't think that would be appropriate in the page on triangular numbers.