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%I #6 Jul 24 2017 19:47:22
%S 1,-1,-3,-165,1337,-356745,31874997,-5714452653,1296863374193,
%T -357091592679441,131690816886952045,-56304582100478416309,
%U 29876409015019700748969,-18379375710670502969514905
%N cos(sec(x)*arctan(x))=1-1/2!*x^2-3/4!*x^4-165/6!*x^6+1337/8!*x^8...
%t With[{nn=30},Take[CoefficientList[Series[Cos[Sec[x]ArcTan[x]],{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Jul 24 2017 *)
%K sign
%O 0,3
%A Patrick Demichel (patrick.demichel(AT)hp.com)