%I #7 Nov 21 2013 12:46:01
%S 1,-1,-19,-565,-24743,-1450985,-100090043,-5608180253,703874231473,
%T 601015521145391,309193460848468125,160230604230030181371,
%U 91310347371287711776777,58721857461984188996135495
%N cos(sec(x)*arctanh(x))=1-1/2!*x^2-19/4!*x^4-565/6!*x^6-24743/8!*x^8...
%t With[{nn=30},Take[CoefficientList[Series[Cos[Sec[x]ArcTanh[x]],{x,0,nn}], x] Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Oct 25 2011 *)
%K sign
%O 0,3
%A Patrick Demichel (patrick.demichel(AT)hp.com)