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A009836
Expansion of tanh(x)*tan(tan(x)).
1
0, 2, 8, 368, 16512, 1583104, 199552000, 36445579264, 8620299812864, 2621816292114432, 987354046567284736, 452732308336619290624, 247917555997339251900416, 159904531672039230122491904
OFFSET
0,2
FORMULA
a(n) ~ (2*n)! * 8 * tanh(arctan(Pi/2)) / ((4 + Pi^2) * arctan(Pi/2)^(2*n+1)). - Vaclav Kotesovec, Jan 24 2015
MATHEMATICA
Tanh[ x ]*Tan[ Tan[ x ] ] (* Even Part *)
nn = 20; Table[(CoefficientList[Series[Tan[Tan[x]]*Tanh[x], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* Vaclav Kotesovec, Jan 24 2015 *)
CROSSREFS
Sequence in context: A220904 A009489 A102597 * A012342 A012348 A219994
KEYWORD
nonn
AUTHOR
EXTENSIONS
Extended and signs tested Mar 15 1997 by Olivier Gérard.
STATUS
approved