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 A360991 #30 Mar 14 2023 12:58:22
%S A360991 1,1,3,8,30,117,533,2599,13919,79620,487810,3167265,21744187,
%T A360991 157020697,1189321019,9417789650,77774264012,668233623419,
%U A360991 5961395449795,55117233908411,527263186773227,5210880621612366,53130216638022540,558176360466846439
%N A360991 Expansion of e.g.f. exp(exp(x) - 1 + x^2/2).
%F A360991 a(0) = a(1) = 1; a(n) = (n-1) * a(n-2) + Sum_{k=1..n} binomial(n-1,k-1) * a(n-k).
%o A360991 (PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(exp(exp(x)-1+x^2/2)))
%Y A360991 Cf. A097514, A355337, A361489.
%K A360991 nonn,easy
%O A360991 0,3
%A A360991 _Seiichi Manyama_, Mar 14 2023