A012570 - OEIS

%I #6 Jul 28 2021 19:21:59

%S 1,-1,13,-277,12185,-840489,84759717,-11842313277,2175505004849,

%T -510170676389457,148514509335632701,-52567147994554822501,

%U 22230968162996350213321,-11070593880057710100740473

%N sech(sinh(x)*cos(x))=1-1/2!*x^2+13/4!*x^4-277/6!*x^6+12185/8!*x^8...

%t With[{nn=30},Take[CoefficientList[Series[Sech[Sinh[x]Cos[x]],{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Jul 28 2021 *)

%K sign

%O 0,3

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