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 A352254 #9 Mar 10 2022 08:26:57
%S A352254 1,1,5,48,753,16880,507579,19509042,927229553,53126200872,
%T A352254 3597373129635,283321938437318,25614466939850169,2629191169850594388,
%U A352254 303549146372282854883,39103024746814973908890,5581172267077778765676129,877211696663645448333041072,151002471269513108372760683523
%N A352254 Expansion of e.g.f. exp( x * sinh(x) / 2 ) (even powers only).
%F A352254 a(0) = 1; a(n) = Sum_{k=1..n} binomial(2*n-1,2*k-1) * k * a(n-k).
%t A352254 nmax = 36; Take[CoefficientList[Series[Exp[x Sinh[x]/2], {x, 0, nmax}], x] Range[0, nmax]!, {1, -1, 2}]
%t A352254 a[0] = 1; a[n_] := a[n] = Sum[Binomial[2 n - 1, 2 k - 1] k a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 18}]
%o A352254 (PARI) my(x='x+O('x^40), v=Vec(serlaplace(exp(x*sinh(x)/2)))); vector(#v\2, k, v[2*k-1]) \\ _Michel Marcus_, Mar 10 2022
%Y A352254 Cf. A000248, A000807, A003724, A003727, A005046, A009233, A351937, A352253.
%K A352254 nonn
%O A352254 0,3
%A A352254 _Ilya Gutkovskiy_, Mar 09 2022