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 A358611 #13 Nov 25 2022 06:34:18
%S A358611 1,1,2,6,24,119,719,5038,40314,362856,3628681,39916081,478996562,
%T A358611 6226980486,87177928344,1307670739319,20922749971919,355686949099438,
%U A358611 6402367478747514,121645013230903656,2432900700505900681,51090921248959468081,1124000372090658580562
%N A358611 a(n) = Sum_{k=0..floor(n/5)} (-1)^k * (n-5*k)!.
%H A358611 Seiichi Manyama, <a href="/A358611/b358611.txt">Table of n, a(n) for n = 0..449</a>
%F A358611 a(n) = n * a(n-1) - a(n-5) + n * a(n-6) for n > 5.
%o A358611 (PARI) a(n) = sum(k=0, n\5, (-1)^k*(n-5*k)!);
%Y A358611 Cf. A358607, A358608, A358609.
%Y A358611 Cf. A358500.
%K A358611 nonn
%O A358611 0,3
%A A358611 _Seiichi Manyama_, Nov 23 2022