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Expansion of e.g.f.: tanh(x)*sin(tan(x)) (even part).
2

%I #23 Sep 17 2022 14:22:54

%S 0,2,-4,38,-3144,-49526,-10349516,-460714706,-91894143376,

%T -6277401116142,-1574511126111380,-81923064774031562,

%U -27289817479229247448,10031662078758108490394,3820037980300331336027556,3713233478960254473261772350,1785602965553070049822150781152

%N Expansion of e.g.f.: tanh(x)*sin(tan(x)) (even part).

%H Stefano Spezia, <a href="/A009834/b009834.txt">Table of n, a(n) for n = 0..200</a>

%t nmax=200; expan=Series[Tanh[x]*Sin[Tan[x]]/2, {x, 0, 2*nmax}]; Join[{0}, Table[(2n)! Coefficient[expan, x^(2n)], {n, nmax}]] (* _Stefano Spezia_, Sep 17 2022 *)

%o (PARI) my(x='x+O('x^50), v=Vec(serlaplace(tanh(x)*sin(tan(x))))); concat(0, vector(#v\2, k, v[2*k-1])) \\ _Michel Marcus_, Sep 17 2022

%Y Twice A024229.

%K sign

%O 0,2

%A _R. H. Hardin_

%E Extended with signs by _Olivier GĂ©rard_, Mar 15 1997