OFFSET
1,1
COMMENTS
REFERENCES
See A180442.
EXAMPLE
a(1) = 24 because 1^2+...+24^2 = 70^2, a(7) = 29 because 7^2+...+29^2 = 92^2.
MATHEMATICA
s[n_, k_]:=Module[{m=n+k-1}, (m(m+1)(2m+1)-n(n-1)(2n-1))/6]; mx=40000; Table[k=2; While[k<mx && !IntegerQ[Sqrt[s[n, k]]], k++]; If[k==mx, 0, n+k-1], {n, 100}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Sep 13 2002
EXTENSIONS
Corrected and extended by Lior Manor Sep 19 2002
Corrected and edited by T. D. Noe, Jan 21 2011
STATUS
approved