A012808 - OEIS

%I #6 Sep 21 2015 17:11:03

%S 1,0,28,-728,54416,-5676352,900432960,-193766436992,55349093955840,

%T -20153308820338688,9138844606925237248,-5050190610067417167872,

%U 3343568694767924711428096,-2613638716122945595362951168

%N arcsinh(sec(x)*arctan(x))=x+28/5!*x^5-728/7!*x^7+54416/9!*x^9...

%t With[{nn=30},Take[CoefficientList[Series[ArcSinh[Sec[x]ArcTan[x]],{x,0,nn}],x] Range[0,nn-1]!,{2,-1,2}]] (* _Harvey P. Dale_, Sep 21 2015 *)

%K sign

%O 0,3

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