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 A356012 #11 Jul 25 2024 14:45:36
%S A356012 1,4,20,60,420,3360,20160,201600,2217600,19958400,259459200,
%T A356012 3632428800,43589145600,697426329600,11856247603200,177843714048000,
%U A356012 3379030566912000,67580611338240000,1216451004088320000,26761922089943040000,615524208068689920000
%N A356012 a(n) = n! / (6 * floor(n/3)).
%F A356012 E.g.f.: -(1 - x^3) * log(1 - x^3)/(6 * (1 - x)).
%t A356012 Table[n!/(6 Floor[n/3]),{n,3,30}] (* _Harvey P. Dale_, Jul 25 2024 *)
%o A356012 (PARI) a(n) = n!/(6*(n\3));
%o A356012 (PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(-(1-x^3)*log(1-x^3)/(6*(1-x))))
%Y A356012 Column 3 of A356013.
%Y A356012 Cf. A355990.
%K A356012 nonn,easy
%O A356012 3,2
%A A356012 _Seiichi Manyama_, Jul 23 2022