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 A031050 #4 Mar 30 2012 18:56:20 %S A031050 4,16,32,48,57,59,61,63,64,65,67,69,71,80,96,112,132,156,180,204,217, %T A031050 220,223,226,228,229,232,235,238,252,276,300,324,348,372,396,409,412, %U A031050 415,418,420,421,424,427,430,444,468,492,516 %N A031050 Position of n-th 4 in A031045. %K A031050 nonn %O A031050 1,1 %A A031050 _Clark Kimberling_