%I #6 Dec 29 2021 12:12:30
%S 1,1,-3,-123,-455,162889,7941813,-647037363,-141890950799,
%T 176381997457,4580546025413229,624311846901265941,
%U -219756895048343473751,-104610854473143576793127
%N sec(sinh(x)*cos(x))=1+1/2!*x^2-3/4!*x^4-123/6!*x^6-455/8!*x^8...
%t With[{nn=30},Take[CoefficientList[Series[Sec[Sinh[x]Cos[x]],{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Dec 29 2021 *)
%K sign
%O 0,3
%A Patrick Demichel (patrick.demichel(AT)hp.com)