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cos(sec(x)*arctanh(x))=1-1/2!*x^2-19/4!*x^4-565/6!*x^6-24743/8!*x^8...
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%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)