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A009696
Expansion of tan(tan(x))*cosh(x) (odd powers only).
1
1, 7, 117, 4555, 317577, 34316335, 5287957053, 1099518892339, 296443784525713, 100546719214082775, 41891900484967019141, 21030561862406486561563, 12519930918307503306140953
OFFSET
1,2
LINKS
FORMULA
a(n) ~ (2*n-1)! * 8 * cosh(arctan(Pi/2)) / ((4+Pi^2) * arctan(Pi/2)^(2*n)). - Vaclav Kotesovec, Jan 23 2015
MAPLE
S:= series(tan(tan(x))*cosh(x), x, 40):
seq(coeff(S, x, j)*j!, j=1..39, 2); # Robert Israel, Feb 19 2018
MATHEMATICA
Tan[ Tan[ x ]]*Cosh[ x ] (* Odd Part *)
nn = 20; Table[(CoefficientList[Series[Cosh[x]*Tan[Tan[x]], {x, 0, 2*nn+1}], x] * Range[0, 2*nn+1]!)[[n]], {n, 2, 2*nn, 2}] (* Vaclav Kotesovec, Jan 23 2015 *)
CROSSREFS
Sequence in context: A299429 A297308 A077394 * A218049 A097202 A163202
KEYWORD
nonn
AUTHOR
EXTENSIONS
Extended and signs tested by Olivier Gérard, Mar 15 1997
Offset changed to 1 by Vaclav Kotesovec, Jan 23 2015
STATUS
approved