A009696 Expansion of tan(tan(x))*cosh(x) (odd powers only).

1, 7, 117, 4555, 317577, 34316335, 5287957053, 1099518892339, 296443784525713, 100546719214082775, 41891900484967019141, 21030561862406486561563, 12519930918307503306140953

Offset

1,2

Links

Robert Israel, Table of n, a(n) for n = 1..225

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

Adjacent sequences: A009693 A009694 A009695 * A009697 A009698 A009699

Keyword

nonn

Author

R. H. Hardin

Extensions

Extended and signs tested by Olivier Gérard, Mar 15 1997

Offset changed to 1 by Vaclav Kotesovec, Jan 23 2015

Status

approved