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 A357147 #11 Sep 15 2022 11:45:22
%S A357147 1,1,1,1,25,481,3241,18481,1332241,44198785,623190961,15416707681,
%T A357147 1602405014761,68167258954081,1598025440555545,134130467333575441,
%U A357147 14793638741719612321,730659540435131811841,34674365632872552887521,5776415685538277157146305
%N A357147 a(n) = n! * Sum_{k=0..floor(n/3)} (n - 3*k)^(3*k)/(n - 3*k)!.
%F A357147 E.g.f.: Sum_{k>=0} x^k / (k! * (1 - (k*x)^3)).
%o A357147 (PARI) a(n) = n!*sum(k=0, n\3, (n-3*k)^(3*k)/(n-3*k)!);
%o A357147 (PARI) my(N=20, x='x+O('x^N)); Vec(serlaplace(sum(k=0, N, x^k/(k!*(1-(k*x)^3)))))
%Y A357147 Cf. A354436, A357146.
%Y A357147 Cf. A353017, A356629.
%K A357147 nonn
%O A357147 0,5
%A A357147 _Seiichi Manyama_, Sep 15 2022