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 A175877 #2 Mar 30 2012 17:26:35
%S A175877 2,4,6,33
%N A175877 Positions of odd terms in A007497.
%C A175877 Corresponding odd terms 3,7,15,564210119465811 (A175878).
%t A175877 n=2;Do[If[OddQ[n=DivisorSigma[1,n]],Print[{k,n}]],{k,2,99}]
%Y A175877 A007497, A175878.
%K A175877 more,nonn
%O A175877 1,1
%A A175877 _Zak Seidov_, Oct 07 2010