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 A358494 #13 Feb 26 2024 10:11:25
%S A358494 1,1,2,6,24,121,722,5046,40344,363000,3629521,39921843,479041932,
%T A358494 6227383740,87181920360,1307714287321,20923268909764,355693655298260,
%U A358494 6402460885833720,121646408103159240,2432922931206035521,51091297862251106885,1124007130194903158430
%N A358494 a(n) = Sum_{k=0..floor(n/5)} (n-4*k)!/k!.
%F A358494 a(n) = (n-1) * a(n-1) + (n-2) * a(n-2) + (n-3) * a(n-3) + (n-4) * a(n-4) + (n-8) * a(n-5) - 4 * a(n-6) - 4 * a(n-7) - 4 * a(n-8) - 4 * a(n-9) + 5 for n > 8.
%F A358494 G.f.: Sum_{k>=0} k! * x^k/(1-x^5)^(k+1). - _Seiichi Manyama_, Feb 26 2024
%o A358494 (PARI) a(n) = sum(k=0, n\5, (n-4*k)!/k!);
%Y A358494 Cf. A000522, A003470, A357949, A358493.
%K A358494 nonn,easy
%O A358494 0,3
%A A358494 _Seiichi Manyama_, Nov 19 2022