%I #7 Dec 08 2018 19:37:13
%S 1,-6,176,-12016,1469696,-280971776,77198422016,-28793654081536,
%T 13988424620507136,-8578076577450295296,6478101995566379565056,
%U -5906079803365219349037056,6394716233788355978540875776
%N tanh(arctan(tanh(x)))=x-6/3!*x^3+176/5!*x^5-12016/7!*x^7...
%t With[{nn=30},Take[CoefficientList[Series[Tanh[ArcTan[Tanh[x]]],{x,0,nn}],x] Range[0,nn-1]!,{2,-1,2}]] (* _Harvey P. Dale_, Dec 08 2018 *)
%Y Cf. A101921.
%K sign
%O 0,2
%A Patrick Demichel (patrick.demichel(AT)hp.com)
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