A012206 - OEIS

%I #6 Nov 28 2016 17:47:46

%S 1,-3,49,-1859,119617,-10283171,678311217,246695568861,

%T -270153706006015,221300400903581245,-191103844337252819535,

%U 185242544952868387351165,-204711474044267911803243455

%N sinh(arctan(arctan(x)))=x-3/3!*x^3+49/5!*x^5-1859/7!*x^7+119617/9!*x^9...

%t With[{nn=30},Take[CoefficientList[Series[Sinh[ArcTan[ArcTan[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)