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 A031220 #4 Mar 30 2012 18:56:21 %S A031220 6,16,26,36,46,47,49,52,55,58,62,77,92,107,121,122,124,127,130,133, %T A031220 137,152,167,182,196,197,199,202,205,208,212,227,242,257,271,272,274, %U A031220 277,280,283,287,302,317,332,346,347,348,350,351 %N A031220 Position of n-th 0 in A031219. %K A031220 nonn %O A031220 1,1 %A A031220 _Clark Kimberling_