A024280 - OEIS

%I #9 Apr 02 2017 15:34:50

%S 0,1,8,16,-9472,-1073024,-73802752,6179501056,4687080685568,

%T 1381417658515456,171579748064165888,-115606987957684404224,

%U -118208590165253073928192,-59168959906143078642089984

%N Expansion of tanh(tan(x)^2)/2.

%t With[{nn=30},Take[CoefficientList[Series[Tanh[Tan[x]^2]/2,{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Dec 31 2014 *)

%Y Cf. A009819.

%K sign

%O 0,3

%A _R. H. Hardin_

%E Extended with signs Mar 1997

%E Prior Mathematica program replaced by _Harvey P. Dale_, Dec 31 2014