Is There Only One Integer n That Makes the Sum of Squares a Perfect Square?

[elimqiu]

Show that there is only one integer n ( > 1) such that
[URL]http://latex.codecogs.com/gif.latex?1^2+2^2+\cdots+n^2=\frac{n(n+1)(2n+1)}{6}[/URL]
is a perfect square

 

[RamaWolf]

For n = 24, the sum is 70^2

 

[elimqiu]

It's hard to show that that's the only possible n