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 A357649 #14 Oct 07 2022 15:47:13
%S A357649 1,0,1,9,64,435,3097,24822,232759,2517345,30070954,382827225,
%T A357649 5110770205,71421582024,1049487311485,16286699945853,267145966335088,
%U A357649 4616924929100535,83622792656855125,1578916985654901366,30957723637379211115,628927539690331202661
%N A357649 Expansion of e.g.f. cosh( (exp(3*x) - 1)/3 ).
%F A357649 a(n) = Sum_{k=0..floor(n/2)} 3^(n-2*k) * Stirling2(n,2*k).
%F A357649 a(n) ~ 3^n * exp(n/LambertW(3*n) - n - 1/3) * n^n / (LambertW(3*n)^n * 2*sqrt(1 + LambertW(3*n))). - _Vaclav Kotesovec_, Oct 07 2022
%t A357649 With[{m = 20}, Range[0, m]! * CoefficientList[Series[Cosh[(Exp[3*x] - 1)/3], {x, 0, m}], x]] (* _Amiram Eldar_, Oct 07 2022 *)
%o A357649 (PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(cosh((exp(3*x)-1)/3)))
%o A357649 (PARI) a(n) = sum(k=0, n\2, 3^(n-2*k)*stirling(n, 2*k, 2));
%Y A357649 Cf. A009153, A024430, A357650.
%Y A357649 Cf. A356572.
%K A357649 nonn
%O A357649 0,4
%A A357649 _Seiichi Manyama_, Oct 07 2022