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 A031306 #4 Mar 30 2012 18:56:21 %S A031306 7,24,44,64,84,104,124,131,133,135,137,139,141,143,144,145,147,149, %T A031306 164,184,211,241,271,301,331,361,391,401,404,407,410,413,416,419,421, %U A031306 422,425,428,451,481,511,541,571,601,631,661,691 %N A031306 Position of n-th 7 in A031298. %K A031306 nonn %O A031306 1,1 %A A031306 _Clark Kimberling_