A009809 - OEIS

%I #14 Jan 15 2023 19:23:24

%S 1,-3,-3,49,2905,83589,-334059,-351159815,-39776495567,-2339943411315,

%T 181395497796525,87834301596283969,15443686178950893193,

%U 532878946672338704661,-705534269899082168140347

%N Expansion of tanh(tan(x))*cos(x).

%t With[{nn=30},Take[CoefficientList[Series[Tanh[Tan[x]]*Cos[x] ,{x,0,nn}],x] Range[ 0,nn-1]!,{2,-1,2}]] (* _Harvey P. Dale_, Jan 15 2023 *)

%K sign

%O 0,2

%A _R. H. Hardin_

%E Extended with signs by _Olivier Gérard_, Mar 15 1997

%E Prior Mathematica program removed by _Harvey P. Dale_, Jan 15 2023