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 A354550 #22 Mar 03 2024 16:49:40
%S A354550 1,1,1,4,13,46,241,1156,6889,44668,300241,2328976,18390901,159273544,
%T A354550 1461200833,13995753136,144068872081,1531949061136,17259159775969,
%U A354550 202543867724608,2474236899786781,31633380519660256,417760492214548561,5751414293905728064
%N A354550 Expansion of e.g.f. exp( x * exp(x^2/2) ).
%H A354550 Seiichi Manyama, <a href="/A354550/b354550.txt">Table of n, a(n) for n = 0..518</a>
%F A354550 a(n) = n! * Sum_{k=0..floor(n/2)} (n - 2*k)^k/(2^k * k! * (n - 2*k)!).
%t A354550 With[{nn=30},CoefficientList[Series[Exp[x Exp[x^2/2]],{x,0,nn}],x] Range[0,nn]!] (* _Harvey P. Dale_, Mar 03 2024 *)
%o A354550 (PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(exp(x*(exp(x^2/2)))))
%o A354550 (PARI) a(n) = n!*sum(k=0, n\2, (n-2*k)^k/(2^k*k!*(n-2*k)!));
%Y A354550 Cf. A000248, A354551, A354552.
%Y A354550 Cf. A216688.
%K A354550 nonn
%O A354550 0,4
%A A354550 _Seiichi Manyama_, Aug 18 2022