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 A356820 #14 Mar 13 2025 14:36:06
%S A356820 1,-1,-5,-10,73,1004,5473,-15562,-746447,-9174088,-41916959,823985546,
%T A356820 24629093641,335144105828,1248594602305,-67564407472426,
%U A356820 -2160461588461343,-34957074099518608,-154556217713939903,10500560586914149250,409146670525578079801
%N A356820 Expansion of e.g.f. exp(-x * exp(3*x)).
%F A356820 G.f.: Sum_{k>=0} (-x)^k / (1 - 3*k*x)^(k+1).
%F A356820 a(n) = Sum_{k=0..n} (-1)^k * (3*k)^(n-k) * binomial(n,k).
%t A356820 With[{nn=20},CoefficientList[Series[Exp[-x Exp[3x]],{x,0,nn}],x] Range[0,nn]!] (* _Harvey P. Dale_, Mar 13 2025 *)
%o A356820 (PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(exp(-x*exp(3*x))))
%o A356820 (PARI) my(N=30, x='x+O('x^N)); Vec(sum(k=0, N, (-x)^k/(1-3*k*x)^(k+1)))
%o A356820 (PARI) a(n) = sum(k=0, n, (-1)^k*(3*k)^(n-k)*binomial(n, k));
%Y A356820 Cf. A292952, A356813, A356819.
%K A356820 sign
%O A356820 0,3
%A A356820 _Seiichi Manyama_, Aug 29 2022