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 A031040 #4 Mar 30 2012 18:56:20 %S A031040 4,17,33,49,56,58,60,62,64,65,66,68,70,81,97,113,134,158,182,206,217, %T A031040 220,223,226,229,230,232,235,238,254,278,302,326,350,374,398,409,412, %U A031040 415,418,421,422,424,427,430,446,470,494,518 %N A031040 Position of n-th 4 in A031035. %K A031040 nonn %O A031040 1,1 %A A031040 _Clark Kimberling_