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 A031224 #4 Mar 30 2012 18:56:21 %S A031224 4,14,24,34,35,37,39,41,43,44,59,74,89,104,106,109,112,115,118,119, %T A031224 134,149,164,179,181,184,187,190,193,194,209,224,239,254,256,259,262, %U A031224 265,268,269,270,273,276,279,282,284,285,288,291 %N A031224 Position of n-th 4 in A031219. %K A031224 nonn %O A031224 1,1 %A A031224 _Clark Kimberling_