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 A352644 #15 Feb 18 2025 08:56:44
%S A352644 1,2,4,14,64,282,1504,9382,59392,417842,3234304,25854270,222423040,
%T A352644 2039652682,19398688768,195195414998,2058666508288,22509119309922,
%U A352644 257507944431616,3058883865391726,37588692110934016,479523015556635002,6316374397705781248
%N A352644 Expansion of e.g.f. exp(2 * x * cosh(x)).
%F A352644 a(0) = 1; a(n) = 2 * Sum_{k=0..floor((n-1)/2)} (2*k+1) * binomial(n-1,2*k) * a(n-2*k-1).
%F A352644 a(n) = Sum_{k=0..n} 2^k * A185951(n,k). - _Seiichi Manyama_, Feb 18 2025
%t A352644 With[{m = 22}, Range[0, m]! * CoefficientList[Series[Exp[2*x*Cosh[x]], {x, 0, m}], x]] (* _Amiram Eldar_, Mar 26 2022 *)
%o A352644 (PARI) my(N=40, x='x+O('x^N)); Vec(serlaplace(exp(2*x*cosh(x))))
%o A352644 (PARI) a(n) = if(n==0, 1, 2*sum(k=0, (n-1)\2, (2*k+1)*binomial(n-1, 2*k)*a(n-2*k-1)));
%Y A352644 Cf. A003727, A185951, A352645.
%K A352644 nonn
%O A352644 0,2
%A A352644 _Seiichi Manyama_, Mar 25 2022