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 A031256 #4 Mar 30 2012 18:56:21 %S A031256 6,9,11,16,28,39,42,43,45,58,62,65,68,71,73,74,77,78,80,81,83,86,88, %T A031256 89,92,95,103,114,117,118,120,133,148,153,156,163,180,195,199,200,203, %U A031256 220,240,247,251,260,274,278,280,282,286,290,294 %N A031256 Position of n-th 2 in A031253. %K A031256 nonn %O A031256 1,1 %A A031256 _Clark Kimberling_