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 A031090 #4 Mar 30 2012 18:56:20 %S A031090 2,13,28,30,31,32,34,36,38,40,42,44,49,67,85,103,121,139,159,186,208, %T A031090 211,213,214,217,220,223,226,229,232,240,267,294,321,348,375,398,401, %U A031090 402,404,407,410,413,416,419,422,425,428,429 %N A031090 Position of n-th 2 in A031087. %K A031090 nonn %O A031090 1,1 %A A031090 _Clark Kimberling_