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arctan(arctan(tanh(x)))=x-6/3!*x^3+184/5!*x^5-13584/7!*x^7...
0

%I #6 Nov 28 2016 17:59:41

%S 1,-6,184,-13584,1840768,-397140224,124961670144,-54024939321344,

%T 30732245464219648,-22258174840910315520,20000813079319781048320,

%U -21837489688957057049821184,28476242253811580631861166080

%N arctan(arctan(tanh(x)))=x-6/3!*x^3+184/5!*x^5-13584/7!*x^7...

%t With[{nn=30},Take[CoefficientList[Series[ArcTan[ArcTan[Tanh[x]]],{x,0,nn}],x] Range[0,nn-1]!,{2,-1,2}]] (* _Ray Chandler_, Nov 28 2016 *)

%K sign

%O 0,2

%A Patrick Demichel (patrick.demichel(AT)hp.com)