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Make 1+4+ +n^2 perfect square

  1. Sep 7, 2011 #1
    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
     
    Last edited by a moderator: Apr 26, 2017
  2. jcsd
  3. Sep 7, 2011 #2
    For n = 24, the sum is 70^2
     
  4. Sep 8, 2011 #3
    It's hard to show that that's the only possible n
     
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