A012852 - OEIS

%I #6 Aug 07 2022 17:22:25

%S 1,-1,-15,-225,3297,973695,99434577,3364479391,-1767300967487,

%T -640573924497921,-102867079807004495,22939113754550703391,

%U 27513402069157221548193,11830594343212717024871295

%N sech(sec(x)*arctanh(x))=1-1/2!*x^2-15/4!*x^4-225/6!*x^6+3297/8!*x^8...

%t With[{nn=30},Take[CoefficientList[Series[Sech[Sec[x]ArcTanh[x]],{x,0,nn}],x] Range[ 0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Aug 07 2022 *)

%K sign

%O 0,3

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