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 A031223 #4 Mar 30 2012 18:56:21 %S A031223 3,12,22,25,27,29,31,32,33,42,56,71,86,91,94,97,100,101,103,116,131, %T A031223 146,161,166,169,172,175,176,178,191,195,198,201,204,206,207,210,213, %U A031223 216,219,221,222,225,228,231,234,236,237,240,241 %N A031223 Position of n-th 3 in A031219. %K A031223 nonn %O A031223 1,1 %A A031223 _Clark Kimberling_