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 A012725 exp(arctanh(x)*tan(x)) = 1+2/2!*x^2+28/4!*x^4+920/6!*x^6+54416/8!*x^8... 0

%I

%S 1,2,28,920,54416,5056288,678865856,124425704832,29873423298816,

%T 9104340085891584,3435702339713424384,1573394503700675106816,

%U 859935938676055185002496,553085284375423405752918016

%N exp(arctanh(x)*tan(x)) = 1+2/2!*x^2+28/4!*x^4+920/6!*x^6+54416/8!*x^8...

%F a(n) ~ 2 * (2*n-1)! * (4*n)^(tan(1)/2) / GAMMA(tan(1)/2). - _Vaclav Kotesovec_, Oct 24 2013

%t With[{nn=30},Take[CoefficientList[Series[Exp[ArcTanh[x]Tan[x]],{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Mar 25 2013 *)

%K nonn

%O 0,2

%A Patrick Demichel (patrick.demichel(AT)hp.com)

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Last modified December 5 17:42 EST 2019. Contains 329768 sequences. (Running on oeis4.)