%I #15 Mar 18 2023 09:48:31
%S 0,1,12,344,18496,1617152,209249792,37538874368,8908210487296,
%T 2699849585000448,1017035120794927104,466006356701359898624,
%U 255181639297776949919744,164564302025304936925888512
%N Expansion of e.g.f. tan(x)*tan(tan(x))/2 (even powers only).
%t With[{nn=30},Take[CoefficientList[Series[Tan[x]Tan[Tan[x]]/2,{x,0,nn}],x] Range[ 0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Mar 18 2023 *)
%o (PARI) x='x+O('x^40); v=Vec(serlaplace(tan(x)*tan(tan(x))/2)); concat([0], vector(#v\2, n, v[2*n-1])) \\ _Michel Marcus_, Mar 13 2019
%Y Cf. A009750.
%K nonn
%O 0,3
%A _R. H. Hardin_
%E Extended and signs tested March 1997.
%E Name edited by _Michel Marcus_, Mar 13 2019
%E Prior Mathematica program replaced by _Harvey P. Dale_, Mar 18 2023