A013178 - OEIS

%I #6 Nov 29 2016 08:46:29

%S 2,-16,816,-100224,23046912,-8501907456,4600667731968,

%T -3432263151550464,3376634004034486272,-4235408050319799091200,

%U 6597340706535893925101568,-12493980287273651231218728960

%N arctan(arctanh(x)+arctan(x))=2*x-16/3!*x^3+816/5!*x^5-100224/7!*x^7...

%t With[{nn=30},Take[CoefficientList[Series[ArcTan[ArcTanh[x]+ArcTan[x]],{x,0,nn}],x] Range[0,nn-1]!,{2,-1,2}]] (* _Ray Chandler_, Nov 29 2016 *)

%K sign

%O 0,1

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