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 A081159 #7 Jan 11 2024 09:09:14 %S A081159 0,0,2,20,148,986,5918,34708,202664 %N A081159 Number of even cycles in range [A014137(2n)..A014138(2n)] of permutation A057505/A057506, with no fixed points of either A057163 or A057164. %F A081159 a(n) = A081157(2n+1). %Y A081159 Cf. A081157, A014137, A014138, A057505, A057506, A057163, A057164. %K A081159 nonn,more %O A081159 0,3 %A A081159 _Wouter Meeussen_ and _Antti Karttunen_, Mar 10 2003