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 A031049 #4 Mar 30 2012 18:56:20 %S A031049 3,14,30,41,43,45,46,47,49,51,53,55,62,78,94,110,129,153,177,193,196, %T A031049 199,201,202,205,208,211,214,225,249,273,297,321,345,369,385,388,391, %U A031049 393,394,397,400,403,406,417,441,465,489,506 %N A031049 Position of n-th 3 in A031045. %K A031049 nonn %O A031049 1,1 %A A031049 _Clark Kimberling_