OFFSET
0,3
FORMULA
a(n) ~ n! * 4 * ((-1)^(n+1) + exp(2*arctan(Pi/2))) /((4+Pi^2) * exp(arctan(Pi/2)) * arctan(Pi/2)^(n+1)). - Vaclav Kotesovec, Jan 23 2015
MATHEMATICA
Tan[ Tan[ x ] ]*Exp[ x ]
CoefficientList[Series[E^x*Tan[Tan[x]], {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Jan 23 2015 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
Extended and signs tested Mar 15 1997 by Olivier Gérard.
STATUS
approved