%I #6 Nov 29 2016 10:22:50
%S 1,4,80,4480,462080,77248000,18902835200,6385348403200,
%T 2843287396352000,1614575957622784000,1138477316012441600000,
%U 976037590707833405440000,999765439694232249958400000
%N sec(arctanh(x)+arctan(x))=1+4/2!*x^2+80/4!*x^4+4480/6!*x^6...
%t With[{nn=30},Take[CoefficientList[Series[Sec[ArcTanh[x]+ArcTan[x]],{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Ray Chandler_, Nov 29 2016 *)
%K nonn
%O 0,2
%A Patrick Demichel (patrick.demichel(AT)hp.com)