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 A031043 #4 Mar 30 2012 18:56:20 %S A031043 7,23,39,55,71,87,103,104,106,108,110,112,114,116,118,119,143,167,191, %T A031043 215,239,263,287,289,292,295,298,301,304,307,310,311,335,359,383,407, %U A031043 431,455,479,481,484,487,490,493,496,499,502 %N A031043 Position of n-th 7 in A031035. %K A031043 nonn %O A031043 1,1 %A A031043 _Clark Kimberling_