A012679 - OEIS

%I #6 Jun 16 2017 18:34:08

%S 2,-16,560,-39296,4526848,-774871040,184332195840,-58099536592896,

%T 23416511012143104,-11741974762852974592,7167152797622391013376,

%U -5231209742433608374681600,4498538959739976198689652736

%N tan(tanh(x)*arctan(x))=2/2!*x^2-16/4!*x^4+560/6!*x^6-39296/8!*x^8...

%t With[{nn=30},Take[CoefficientList[Series[Tan[Tanh[x]ArcTan[x]],{x,0,nn}],x] Range[0,nn]!,{3,-1,2}]] (* _Harvey P. Dale_, Jun 16 2017 *)

%K sign

%O 0,1

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