%I #6 Nov 28 2016 17:53:24
%S 1,1,-15,609,-48031,6247681,-1214813487,330587407201,-120086685689663,
%T 56186566871496961,-32929237073496552527,23637878950680710828385,
%U -20404361373477159717443295
%N cosh(arctan(arctan(x)))=1+1/2!*x^2-15/4!*x^4+609/6!*x^6-48031/8!*x^8...
%t With[{nn=30},Take[CoefficientList[Series[Cosh[ArcTan[ArcTan[x]]],{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Ray Chandler_, Nov 28 2016 *)
%K sign
%O 0,3
%A Patrick Demichel (patrick.demichel(AT)hp.com)
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