A009684 Expansion of tan(sinh(x))/cos(x) (odd powers only).

1, 6, 92, 2744, 135568, 10052064, 1046433728, 145777470848, 26210435272960, 5912584665282048, 1635801299492215808, 544795386333006067712, 215040848214192589017088, 99279916831031214863081472

Offset

1,2

Links

Table of n, a(n) for n=1..14.

Formula

a(n) ~ (2*n-1)! * 4 / (sqrt(4+Pi^2) * cos(arcsinh(Pi/2)) * arcsinh(Pi/2)^(2*n)). - Vaclav Kotesovec, Jan 23 2015

Mathematica

Tan[ Sinh[ x ]]/Cos[ x ] (* Odd Part *)
nn = 20; Table[(CoefficientList[Series[Sec[x]*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

Sequence in context: A280214 A113266 A009607 * A221080 A009527 A053512

Adjacent sequences: A009681 A009682 A009683 * A009685 A009686 A009687

Keyword

nonn

Author

R. H. Hardin

Extensions

Extended and signs tested Mar 15 1997 by Olivier Gérard.

Offset changed to 1 by Vaclav Kotesovec, Jan 23 2015

Status

approved