A012447 - OEIS

%I #8 Nov 28 2016 18:43:21

%S 0,2,0,-80,-2688,260608,2928640,-463763456,-517376835584,

%T 108823739498496,-2683131538178048,5868236283429519360,

%U -6862655376791380688896,2738386568702639562817536

%N arctan(arctan(x)*tan(x))=2/2!*x^2-80/6!*x^6-2688/8!*x^8+260608/10!*x^10...

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

%K sign

%O 0,2

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