A009751 - OEIS

%I #25 Feb 13 2018 04:14:54

%S 0,2,8,48,2176,72704,2567168,320538624,23648567296,2869964963840,

%T 550752408829952,81617924549246976,20769854695130791936,

%U 5449382125873097867264,1599364150040158382587904,573113440182309263706685440,238664184536900397410937733120

%N Expansion of e.g.f. tan(x)*tan(tanh(x)), even powers only.

%H G. C. Greubel, <a href="/A009751/b009751.txt">Table of n, a(n) for n = 0..240</a> (terms 0..100 from Vincenzo Librandi)

%t With[{nn=30},Take[CoefficientList[Series[Tan[x]*Tan[Tanh[x]],{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Feb 07 2014 *)

%o (PARI) x='x+O('x^50); v=Vec(serlaplace(tan(x)*tan(tanh(x)))); concat([0], vector(#v\2,n,v[2*n-1])) \\ _G. C. Greubel_, Feb 12 2018

%K nonn

%O 0,2

%A _R. H. Hardin_

%E Extended and signs tested by _Olivier Gérard_, Mar 15 1997

%E Prior Mathematica program replaced by and one more term from _Harvey P. Dale_, Feb 07 2014