A012847 - OEIS

%I #6 Apr 16 2019 12:05:17

%S 1,4,28,152,6928,2225408,348750400,38567316608,5024551512320,

%T 2238520490011648,1265695140964379648,555587429710072952832,

%U 218348017328527789264896,124784882666107086189330432

%N arcsinh(sec(x)*arctanh(x))=x+4/3!*x^3+28/5!*x^5+152/7!*x^7+6928/9!*x^9...

%t With[{nn=30},Take[CoefficientList[Series[ArcSinh[Sec[x]ArcTanh[x]],{x,0,nn}],x] Range[0,nn-1]!,{2,-1,2}]] (* _Harvey P. Dale_, Apr 16 2019 *)

%K nonn

%O 0,2

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