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 A355988 #12 Jul 22 2022 10:13:39
%S A355988 1,1,2,6,24,120,360,2520,20160,60480,604800,6652800,19958400,
%T A355988 259459200,3632428800,10897286400,174356582400,2964061900800,
%U A355988 8892185702400,168951528345600,3379030566912000,10137091700736000,223016017416192000,5129368400572416000
%N A355988 a(n) = n! / floor(n/3)!.
%F A355988 E.g.f.: (1 - x^3) * exp(x^3)/(1 - x).
%t A355988 a[n_] := n!/Floor[n/3]!; Array[a, 24, 0] (* _Amiram Eldar_, Jul 22 2022 *)
%o A355988 (PARI) a(n) = n!/(n\3)!;
%o A355988 (PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace((1-x^3)*exp(x^3)/(1-x)))
%Y A355988 Cf. A081125, A355990.
%K A355988 nonn,easy
%O A355988 0,3
%A A355988 _Seiichi Manyama_, Jul 22 2022