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 A047677 #16 Mar 07 2020 01:35:54 %S A047677 2,4,24,288,5760,172800,7257600,406425600,29262643200,2633637888000, %T A047677 289700167680000,38240422133760000,5965505852866560000, %U A047677 1085722065221713920000,228001633696559923200000,54720392087174381568000000,14883946647711431786496000000 %N A047677 Row 2 of square array defined in A047675: 2*n!*(n+1)!. %C A047677 a(n) = A152877(2n+1, 2n-2) for n > 0. - _Alois P. Heinz_, Nov 10 2013 %p A047677 a:= proc(n) a(n):= `if`(n=0, 2, n*(n+1) * a(n-1)) end: %p A047677 seq(a(n), n=0..20); # _Alois P. Heinz_, Nov 11 2013 %t A047677 2*Times@@@Partition[Range[0,20]!,2,1] (* _Harvey P. Dale_, Sep 25 2017 *) %Y A047677 Cf. A047675, A010790, A152877. %K A047677 nonn %O A047677 0,1 %A A047677 _N. J. A. Sloane_