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 A031012 #4 Mar 30 2012 18:56:19 %S A031012 4,15,29,43,50,52,54,56,57,58,60,62,71,85,103,124,145,166,176,179,182, %T A031012 185,187,188,191,194,208,229,250,271,292,313,323,326,329,332,334,335, %U A031012 338,341,355,376,397,418,439,460,470,473,476 %N A031012 Position of n-th 4 in A031007. %K A031012 nonn %O A031012 1,1 %A A031012 _Clark Kimberling_