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 A151585 #3 Mar 31 2012 12:35:18 %S A151585 0,3,976,44275,1046556,18098871,262962368,3438697635,42050013500 %N A151585 Number of permutations of 2 indistinguishable copies of 1..n arranged in a circle with exactly 4 adjacent element pairs in decreasing order. %K A151585 nonn %O A151585 2,2 %A A151585 _R. H. Hardin_ May 21 2009