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 A151587 #5 Dec 27 2023 22:56:28 %S A151587 0,4,11565,2580588,229630758,12719963448,531411968223,18510889687040 %N A151587 Number of permutations of 2 indistinguishable copies of 1..n arranged in a circle with exactly 6 adjacent element pairs in decreasing order. %K A151587 nonn %O A151587 3,2 %A A151587 _R. H. Hardin_, May 21 2009