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 A031304 #4 Mar 30 2012 18:56:21 %S A031304 5,20,40,60,80,91,93,95,97,99,100,101,103,105,107,109,120,140,160,180, %T A031304 205,235,265,295,325,341,344,347,350,353,355,356,359,362,365,368,385, %U A031304 415,445,475,505,535,565,595,625,641,644,647 %N A031304 Position of n-th 5 in A031298. %K A031304 nonn %O A031304 1,1 %A A031304 _Clark Kimberling_