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 A367937 #9 Dec 07 2023 08:23:14
%S A367937 1,7,53,431,3741,34471,335621,3438943,36954285,415187415,4864054165,
%T A367937 59278367247,749926582717,9829744447495,133267495918885,
%U A367937 1865916660838847,26942271261464525,400673643394972983,6129834703935247285,96368617886967750767,1555302323744129219293
%N A367937 Expansion of e.g.f. exp(4*(exp(x) - 1) + 3*x).
%F A367937 G.f. A(x) satisfies: A(x) = 1 + x * ( 3 * A(x) + 4 * A(x/(1 - x)) / (1 - x) ).
%F A367937 a(n) = exp(-4) * Sum_{k>=0} 4^k * (k+3)^n / k!.
%F A367937 a(0) = 1; a(n) = 3 * a(n-1) + 4 * Sum_{k=1..n} binomial(n-1,k-1) * a(n-k).
%t A367937 nmax = 20; CoefficientList[Series[Exp[4 (Exp[x] - 1) + 3 x], {x, 0, nmax}], x] Range[0, nmax]!
%t A367937 a[0] = 1; a[n_] := a[n] = 3 a[n - 1] + 4 Sum[Binomial[n - 1, k - 1] a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 20}]
%o A367937 (PARI) my(x='x+O('x^30)); Vec(serlaplace(exp(4*(exp(x) - 1) + 3*x))) \\ _Michel Marcus_, Dec 07 2023
%Y A367937 Cf. A005494, A035009, A078945, A355252, A366199, A367889.
%K A367937 nonn
%O A367937 0,2
%A A367937 _Ilya Gutkovskiy_, Dec 05 2023