%I #9 Aug 22 2017 17:07:42

%S 0,1,0,-24,448,-640,-658944,56992768,-2831024128,-86998155264,

%T 51519425740800,-9075812362878976,917148920337924096,

%U 26667007293767286784,-33058738844745936666624,2573727989288825813729280,4259701574179331481681264640

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

%t With[{nn=30},Take[CoefficientList[Series[Tan[Tanh[x]]*x/2,{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Aug 22 2017 *)

%Y Cf. A009718.

%K sign

%O 0,4

%A _R. H. Hardin_

%E Extended with signs Mar 1997

%E More terms from and prior Mathematica program replaced by _Harvey P. Dale_, Aug 22 2017