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 A081158 #9 Jan 11 2024 09:03:34 %S A081158 0,0,0,8,60,402,2474,14496,84282,492048 %N A081158 Number of even cycles in range [A014137(2n-1)..A014138(2n-1)] of permutation A057505/A057506, with no fixed points of A057164. %F A081158 a(n) = A081157(2n) = A081151(n) - A001700(n-1) [where A001700(-1) is taken as 0 here]. %Y A081158 Cf. A081157, A081151, A001700. %Y A081158 Cf. A014137, A014138, A057505, A057506, A057164. %K A081158 nonn,more %O A081158 0,4 %A A081158 _Wouter Meeussen_ and _Antti Karttunen_, Mar 10 2003