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 A031315 #4 Mar 30 2012 18:56:23 %S A031315 16,18,20,22,24,127,130,133,136,139,246,249,252,255,258,261,264,267, %T A031315 270,273,276,277,279,280,282,283,285,286,288,289,291,294,297,300,303, %U A031315 306,309,312,315,318,321,324,327,330,333,336,339 %N A031315 Position of n-th 2 in A031312. %K A031315 nonn %O A031315 1,1 %A A031315 _Clark Kimberling_