A013464 - OEIS

%I #6 Nov 29 2016 11:01:41

%S 0,-4,0,-1440,35840,-7257600,790732800,-208797388800,48099557376000,

%T -19670079356928000,7390762646372352000,-4427057815048028160000,

%U 2474680614543006105600000,-2020995311309719496294400000

%N arctan(arctan(x)-arctanh(x))=-4/3!*x^3-1440/7!*x^7+35840/9!*x^9...

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

%K sign

%O 0,2

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