%I #6 Mar 22 2023 17:52:04
%S 1,0,0,-90,2520,-368550,36798300,-8485126650,1746971226000,
%T -623950950372750,216093789514102500,-111905269600936061250,
%U 58297381976449590975000,-41488228251938936311593750
%N sech(arcsin(x)-arctan(x))=1-90/6!*x^6+2520/8!*x^8-368550/10!*x^10...
%t With[{nn=30},Take[CoefficientList[Series[Sech[ArcSin[x]-ArcTan[x]],{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Mar 22 2023 *)
%K sign
%O 0,4
%A Patrick Demichel (patrick.demichel(AT)hp.com)