%I #6 Jul 04 2017 12:11:03
%S 1,-1,-3,-21,185,67159,11805621,2380474563,591392066161,
%T 181472052075695,68002767860495981,30687549807072450459,
%U 16452262725440109947177,10350119384788050029211399
%N cos(sin(arctanh(x)))=1-1/2!*x^2-3/4!*x^4-21/6!*x^6+185/8!*x^8...
%t With[{nn=30},Take[CoefficientList[Series[Cos[Sin[ArcTanh[x]]],{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Jul 04 2017 *)
%K sign
%O 0,3
%A Patrick Demichel (patrick.demichel(AT)hp.com)