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I'm trying to find Triangular numbers that are also square. So $m^2=\frac{n(n+1)}{2}$
I don't want the actual answer with the solution but I'd like to solve the problem myself : I need some clues to take me on the right track.


marked as duplicate by Dietrich Burde, Matthew Conroy, Community Mar 31 '17 at 15:50

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  • $\begingroup$ Are you familiar with Pell's equation and methods of solving equations of that form? en.wikipedia.org/wiki/Pell's_equation $\endgroup$ – Matthew Conroy Mar 30 '17 at 19:02
  • $\begingroup$ No. But now I can learn Pell's equation. $\endgroup$ – Andrea Mar 30 '17 at 19:05
  • $\begingroup$ You're welcome! $\endgroup$ – Matthew Conroy Mar 30 '17 at 19:06
  • $\begingroup$ This question also offers a great triangular-square insight. $\endgroup$ – Dietrich Burde Mar 30 '17 at 19:14