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 A356827 #17 Dec 04 2023 06:29:10
%S A356827 1,1,7,46,361,3436,37729,463366,6280369,93015352,1491337441,
%T A356827 25684077706,472217487625,9221588527204,190441412508481,
%U A356827 4143470377262806,94663498086222049,2264440394856702832,56570146384760433217,1472545685988162638722
%N A356827 Expansion of e.g.f. exp(x * exp(3*x)).
%F A356827 G.f.: Sum_{k>=0} x^k / (1 - 3*k*x)^(k+1).
%F A356827 a(n) = Sum_{k=0..n} (3*k)^(n-k) * binomial(n,k).
%p A356827 A356827 := proc(n)
%p A356827 add((3*k)^(n-k) * binomial(n,k),k=0..n) ;
%p A356827 end proc:
%p A356827 seq(A356827(n),n=0..70) ; # _R. J. Mathar_, Dec 04 2023
%o A356827 (PARI) my(N=20, x='x+O('x^N)); Vec(serlaplace(exp(x*exp(3*x))))
%o A356827 (PARI) my(N=20, x='x+O('x^N)); Vec(sum(k=0, N, x^k/(1-3*k*x)^(k+1)))
%o A356827 (PARI) a(n) = sum(k=0, n, (3*k)^(n-k)*binomial(n, k));
%Y A356827 Cf. A000248, A003725, A216689, A295552.
%Y A356827 Cf. A277456, A336951, A351737, A355501, A356820.
%K A356827 nonn
%O A356827 0,3
%A A356827 _Seiichi Manyama_, Aug 29 2022