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 A031238 #4 Mar 30 2012 18:56:21 %S A031238 2,9,16,18,19,20,22,24,29,39,51,66,76,79,81,82,85,88,96,111,122,125, %T A031238 126,128,131,134,137,140,141,143,146,149,151,152,154,155,156,157,158, %U A031238 160,161,163,164,167,170,171,173,176,179,182,185 %N A031238 Position of n-th 2 in A031235. %K A031238 nonn %O A031238 1,1 %A A031238 _Clark Kimberling_