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 A336948 #11 Aug 09 2021 03:47:57
%S A336948 1,4,23,195,2229,31863,546255,10925757,249753897,6422808411,
%T A336948 183524701779,5768419379913,197791542799965,7347180526444359,
%U A336948 293912722687075767,12597352573293062757,575928946256877156177,27976119070974574461363,1438896686251112024068251
%N A336948 E.g.f.: 1 / (exp(-3*x) - x).
%F A336948 a(n) = n! * Sum_{k=0..n} (3 * (n-k+1))^k / k!.
%F A336948 a(0) = 1; a(n) = 4 * n * a(n-1) - Sum_{k=2..n} binomial(n,k) * (-3)^k * a(n-k).
%F A336948 a(n) ~ n! / ((1 + LambertW(3)) * (LambertW(3)/3)^(n+1)). - _Vaclav Kotesovec_, Aug 09 2021
%t A336948 nmax = 18; CoefficientList[Series[1/(Exp[-3 x] - x), {x, 0, nmax}], x] Range[0, nmax]!
%t A336948 Table[n! Sum[(3 (n - k + 1))^k/k!, {k, 0, n}], {n, 0, 18}]
%t A336948 a[0] = 1; a[n_] := a[n] = 4 n a[n - 1] - Sum[Binomial[n, k] (-3)^k a[n - k], {k, 2, n}]; Table[a[n], {n, 0, 18}]
%o A336948 (PARI) seq(n)={ Vec(serlaplace(1 / (exp(-3*x + O(x*x^n)) - x))) } \\ _Andrew Howroyd_, Aug 08 2020
%Y A336948 Cf. A072597, A328182, A336947, A336949, A336951.
%K A336948 nonn
%O A336948 0,2
%A A336948 _Ilya Gutkovskiy_, Aug 08 2020