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 A336961 #6 Mar 01 2023 14:18:31
%S A336961 1,2,10,56,384,3022,26626,258624,2734360,31168682,380196414,
%T A336961 4932536908,67717987948,979613124414,14877703575130,236469561581768,
%U A336961 3922587278751504,67743812585483218,1215417753459838198,22609895367286957572,435341977596130683316
%N A336961 Expansion of e.g.f. exp(x * (2 + x) * exp(x)).
%C A336961 Exponential transform of the oblong numbers (A002378).
%F A336961 E.g.f.: exp(x * (2 + x) * exp(x)).
%F A336961 a(0) = 1; a(n) = Sum_{k=1..n} binomial(n-1,k-1) * k * (k + 1) * a(n-k).
%t A336961 nmax = 20; CoefficientList[Series[Exp[x (2 + x) Exp[x]], {x, 0, nmax}], x] Range[0, nmax]!
%t A336961 a[0] = 1; a[n_] := a[n] = Sum[Binomial[n - 1, k - 1] k (k + 1) a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 20}]
%Y A336961 Cf. A000248, A002378, A033462, A209801, A216507, A279361, A336960.
%K A336961 nonn
%O A336961 0,2
%A A336961 _Ilya Gutkovskiy_, Aug 09 2020