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 A339017 #10 Nov 20 2020 21:38:27
%S A339017 1,0,0,0,2,2,2,2,142,506,1346,3170,53198,375234,1880738,7919082,
%T A339017 72104190,678488362,5164781154,33220643026,271431061614,2710340281426,
%U A339017 26278673924322,228727591600826,2081516848032222,21560234032116154,236863265302626722,2521687569105476002
%N A339017 E.g.f.: exp(2 * (exp(x) - 1 - x - x^2 / 2 - x^3 / 6)).
%H A339017 Seiichi Manyama, <a href="/A339017/b339017.txt">Table of n, a(n) for n = 0..569</a>
%F A339017 a(0) = 1; a(n) = 2 * Sum_{k=4..n} binomial(n-1,k-1) * a(n-k).
%F A339017 a(n) = Sum_{k=0..n} binomial(n,k) * A057837(k) * A057837(n-k).
%t A339017 nmax = 27; CoefficientList[Series[Exp[2 (Exp[x] - 1 - x - x^2/2 - x^3/6)], {x, 0, nmax}], x] Range[0, nmax]!
%t A339017 a[0] = 1; a[n_] := a[n] = 2 Sum[Binomial[n - 1, k - 1] a[n - k], {k, 4, n}]; Table[a[n], {n, 0, 27}]
%o A339017 (PARI) my(x='x+O('x^30)); Vec(serlaplace(exp(2*(exp(x) - 1 - x - x^2/2 - x^3/6)))) \\ _Michel Marcus_, Nov 19 2020
%Y A339017 Cf. A001861, A057837, A194689, A339014, A339027.
%K A339017 nonn
%O A339017 0,5
%A A339017 _Ilya Gutkovskiy_, Nov 19 2020