OFFSET
0,2
FORMULA
a(n) ~ (2*n)! * 8 / ((4+Pi^2) * arctan(Pi/2)^(2*n)). - Vaclav Kotesovec, Jan 23 2015
MATHEMATICA
With[{nn=30}, Take[CoefficientList[Series[Tan[Tan[x]]*x , {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Jun 08 2014 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Extended and signs tested Mar 15 1997 by Olivier Gérard.
Previous Mathematica program replaced by Harvey P. Dale, Jun 08 2014
STATUS
approved