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 A031303 #4 Mar 30 2012 18:56:21 %S A031303 4,18,38,58,71,73,75,77,78,79,81,83,85,87,89,98,118,138,158,178,202, %T A031303 232,262,292,311,314,317,320,322,323,326,329,332,335,338,352,382,412, %U A031303 442,472,502,532,562,592,611,614,617,620,622,623 %N A031303 Position of n-th 4 in A031298. %K A031303 nonn %O A031303 1,1 %A A031303 _Clark Kimberling_