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 A367786 #6 Dec 01 2023 15:59:17
%S A367786 1,3,25,235,2737,36947,563657,9542715,176920417,3555369635,
%T A367786 76820077945,1772943290763,43469116126737,1127040956393203,
%U A367786 30779951676185385,882453651485815003,26480355971228530369,829522636694530362691,27064267045022876869337,917751849133986186857003
%N A367786 Expansion of e.g.f. exp(exp(4*x) - x - 1).
%F A367786 a(n) = exp(-1) * Sum_{k>=0} (4*k-1)^n / k!.
%F A367786 a(0) = 1; a(n) = -a(n-1) + Sum_{k=1..n} binomial(n-1,k-1) * 4^k * a(n-k).
%F A367786 a(n) = Sum_{k=0..n} (-1)^(n-k) * binomial(n,k) * 4^k * Bell(k).
%t A367786 nmax = 19; CoefficientList[Series[Exp[Exp[4 x] - x - 1], {x, 0, nmax}], x] Range[0, nmax]!
%t A367786 a[0] = 1; a[n_] := a[n] = -a[n - 1] + Sum[Binomial[n - 1, k - 1] 4^k a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 19}]
%t A367786 Table[Sum[(-1)^(n - k) Binomial[n, k] 4^k BellB[k], {k, 0, n}], {n, 0, 19}]
%o A367786 (PARI) my(x='x+O('x^30)); Vec(serlaplace(exp(exp(4*x) - x - 1))) \\ _Michel Marcus_, Nov 30 2023
%Y A367786 Cf. A000110, A000296, A124311, A285064, A285065, A330605, A367785.
%K A367786 nonn
%O A367786 0,2
%A A367786 _Ilya Gutkovskiy_, Nov 30 2023