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 A151584 #3 Mar 31 2012 12:35:18 %S A151584 0,36,1088,14220,134928,1093316,8120064,57280284,391301840 %N A151584 Number of permutations of 2 indistinguishable copies of 1..n arranged in a circle with exactly 3 adjacent element pairs in decreasing order. %K A151584 nonn %O A151584 2,2 %A A151584 _R. H. Hardin_ May 21 2009