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 A346921 #23 May 09 2022 08:38:12
%S A346921 1,0,1,3,17,110,874,8064,85182,1012248,13369026,194245590,3079135806,
%T A346921 52880064588,978038495316,19381794788160,409702099828104,
%U A346921 9201877089355584,218832476773294008,5493266481129425064,145153549897858762776,4027310838211114515600
%N A346921 Expansion of e.g.f. 1 / (1 - log(1 - x)^2 / 2).
%H A346921 Seiichi Manyama, <a href="/A346921/b346921.txt">Table of n, a(n) for n = 0..430</a>
%F A346921 a(0) = 1; a(n) = Sum_{k=1..n} binomial(n,k) * |Stirling1(k,2)| * a(n-k).
%F A346921 a(n) ~ n! * exp(sqrt(2)*n) / (sqrt(2) * (exp(sqrt(2)) - 1)^(n+1)). - _Vaclav Kotesovec_, Aug 08 2021
%F A346921 a(n) = Sum_{k=0..floor(n/2)} (2*k)! * |Stirling1(n,2*k)|/2^k. - _Seiichi Manyama_, May 06 2022
%t A346921 nmax = 21; CoefficientList[Series[1/(1 - Log[1 - x]^2/2), {x, 0, nmax}], x] Range[0, nmax]!
%t A346921 a[0] = 1; a[n_] := a[n] = Sum[Binomial[n, k] Abs[StirlingS1[k, 2]] a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 21}]
%o A346921 (PARI) my(x='x+O('x^25)); Vec(serlaplace(1/(1-log(1-x)^2/2))) \\ _Michel Marcus_, Aug 07 2021
%o A346921 (PARI) a(n) = sum(k=0, n\2, (2*k)!*abs(stirling(n, 2*k, 1))/2^k); \\ _Seiichi Manyama_, May 06 2022
%Y A346921 Cf. A007840, A346922, A346923, A346924.
%Y A346921 Cf. A000254, A052811, A305306, A330047, A347001.
%K A346921 nonn
%O A346921 0,4
%A A346921 _Ilya Gutkovskiy_, Aug 07 2021