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 A375105 #9 Jul 30 2024 14:38:54 %S A375105 1,12,720,107520,30240000,13795246080,9302892318720,8706006083174400, %T A375105 10801536141415219200,17163329863680000000000, %U A375105 33994996578425904640819200,82126085558902590463908249600,237708952408715572102802964480000,812136157489332816782291600670720000 %N A375105 a(n) = (2*n)^(n-2)*(2*n)!/n!. %C A375105 a(n) is the number of spanning trees with a perfect matching in a complete graph with 2*n nodes. See Li et al. in Links. %H A375105 Danyi Li, Xing Feng, and Weigen Yan, <a href="https://doi.org/10.1016/j.dam.2024.07.026">Enumeration of spanning trees with a perfect matching of hexagonal lattices on the cylinder and Möbius strip</a>, Discrete Applied Mathematics, Volume 358, 2024, Pages 320-325. %F A375105 a(n) ~ (1/(2*sqrt(2)))*(8/e)^n*n^(2*(n-1)). %t A375105 a[n_]:=(2n)^(n-2)(2n)!/n!; Array[a,14] %Y A375105 Cf. A000142, A000984, A010050, A020765, A135008. %K A375105 nonn %O A375105 1,2 %A A375105 _Stefano Spezia_, Jul 30 2024