This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A073526 #8 Oct 03 2014 11:20:36
%S A073526 1,2,3,4,5,6,7,8,9,15,16,17,18,19,25,26,27,28,29,30,31,32,33,34,35,36,
%T A073526 37,38,39,40,41,49,75,76,77,91,92,93,94,95,96,97,98,99,125,126,127,
%U A073526 128,129,130,131,132,133,134,135,153,154,155,205,206,207,208,209,210,211
%N A073526 Denominator of Sum_{k=1..n} 1/k^2 is a square.
%F A073526 {n: A007407(n) in A000290} . - _R. J. Mathar_, Oct 03 2014
%t A073526 Select[Range[300],IntegerQ[Sqrt[Denominator[Sum[1/k^2,{k,#}]]]]&] (* _Harvey P. Dale_, Mar 28 2012 *)
%Y A073526 Cf. A007407, A073527.
%K A073526 nonn,easy
%O A073526 1,2
%A A073526 _N. J. A. Sloane_, Aug 30 2002
%E A073526 More terms from _Matthew Conroy_, Sep 09 2002