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 A335982 #6 Jul 04 2020 01:44:31
%S A335982 1,5,21,69,149,69,-619,-187,9365,-3515,-193643,453957,4704917,
%T A335982 -29425595,-83918443,1640246085,-3184430955,-74516517307,604223657877,
%U A335982 1324972362053,-52526078298475,264984579390533,2477371363954069,-44206576595187899,133280843118435477
%N A335982 Expansion of e.g.f. exp(4 * (1 - exp(-x)) + x).
%F A335982 a(n) = exp(4) * (-1)^n * Sum_{k>=0} (-4)^k * (k - 1)^n / k!.
%F A335982 a(0) = 1; a(n) = a(n-1) + 4 * Sum_{k=0..n-1} (-1)^(n-k-1) * binomial(n-1,k) * a(k).
%t A335982 nmax = 24; CoefficientList[Series[Exp[4 (1 - Exp[-x]) + x], {x, 0, nmax}], x] Range[0, nmax]!
%t A335982 a[0] = 1; a[n_] := a[n] = a[n - 1] + 4 Sum[(-1)^(n - k - 1) Binomial[n - 1, k] a[k], {k, 0, n - 1}]; Table[a[n], {n, 0, 24}]
%Y A335982 Cf. A078944, A078945, A109747, A309085, A335868, A335980, A335981.
%K A335982 sign
%O A335982 0,2
%A A335982 _Ilya Gutkovskiy_, Jul 03 2020