OFFSET
1,2
FORMULA
a(n) ~ (2*n-1)! * 8 / ((4+Pi^2) * sqrt(1+arctan(Pi/2)^2) * arcsinh(arctan(Pi/2))^(2*n)). - Vaclav Kotesovec, Jan 23 2015
MATHEMATICA
Tan[ Tan[ Sinh[ x ] ] ] (* Odd Part *)
nn = 20; Table[(CoefficientList[Series[Tan[Tan[Sinh[x]]], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* Vaclav Kotesovec, Jan 23 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Extended and signs tested Mar 15 1997 by Olivier Gérard.
Offset changed to 1 by Vaclav Kotesovec, Jan 23 2015
STATUS
approved