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 A343707 #9 Oct 20 2021 07:49:28
%S A343707 1,3,15,113,1145,14539,221663,3943281,80173345,1833831619,46606646175,
%T A343707 1302954958689,39737420405753,1312901360002283,46714233470065999,
%U A343707 1780859204826798401,72416689888874547969,3128792006916853876291,143132514626658326870767,6911638338982428907738641
%N A343707 a(n) = 1 + 2 * Sum_{k=0..n-1} binomial(n,k) * (n-k-1)! * a(k).
%H A343707 Seiichi Manyama, <a href="/A343707/b343707.txt">Table of n, a(n) for n = 0..389</a>
%F A343707 E.g.f.: exp(x) / (1 + 2 * log(1 - x)).
%F A343707 a(n) = Sum_{k=0..n} binomial(n,k) * A088500(k).
%t A343707 a[n_] := a[n] = 1 + 2 Sum[Binomial[n, k] (n - k - 1)! a[k], {k, 0, n - 1}]; Table[a[n], {n, 0, 19}]
%t A343707 nmax = 19; CoefficientList[Series[Exp[x]/(1 + 2 Log[1 - x]), {x, 0, nmax}], x] Range[0, nmax]!
%o A343707 (PARI) N=20; x='x+O('x^N); Vec(serlaplace(exp(x)/(1+2*log(1-x)))) \\ _Seiichi Manyama_, Oct 20 2021
%Y A343707 Cf. A088500, A201339, A291979, A343709, A343710.
%K A343707 nonn
%O A343707 0,2
%A A343707 _Ilya Gutkovskiy_, Apr 26 2021