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 A380228 #10 Jan 17 2025 09:05:25
%S A380228 1,1,4,21,139,1108,10287,108699,1285228,16783395,239571125,3706900992,
%T A380228 61746357449,1100827515921,20902202270580,420903243601485,
%U A380228 8955301860908499,200664408693149164,4721693823656357303,116370390417335016731,2997078741899026174972,80492590654279893652283
%N A380228 Expansion of e.g.f. exp( exp( (exp(2*x)-1)/2 ) - 1 ).
%F A380228 a(n) = Sum_{k=0..n} 2^(n-k) * Stirling2(n,k) * Bell(k).
%o A380228 (PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(exp(exp((exp(2*x)-1)/2)-1)))
%Y A380228 Cf. A000258, A380229.
%Y A380228 Cf. A346417.
%K A380228 nonn
%O A380228 0,3
%A A380228 _Seiichi Manyama_, Jan 17 2025