A009699 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

A009699

Expansion of tan(tan(x))*sinh(x).

0, 2, 20, 518, 27432, 2405194, 312554428, 56240197198, 13369846932560, 4056020122211730, 1528702557462347620, 700644649971815625622, 383722595185095053746040, 247477546043660240025524954

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,2

LINKS

Table of n, a(n) for n=0..13.

FORMULA

a(n) ~ (2*n)! * 8 * sinh(arctan(Pi/2)) / ((4+Pi^2) * arctan(Pi/2)^(2*n+1)). - Vaclav Kotesovec, Jan 23 2015

MATHEMATICA

Tan[ Tan[ x ] ]*Sinh[ x ] (* Even Part *)

nn = 20; Table[(CoefficientList[Series[Sinh[x]*Tan[Tan[x]], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* Vaclav Kotesovec, Jan 23 2015 *)

CROSSREFS

Sequence in context: A168136 A103353 A009344 * A101927 A341269 A157317

Adjacent sequences: A009696 A009697 A009698 * A009700 A009701 A009702

KEYWORD

nonn

AUTHOR

R. H. Hardin

EXTENSIONS

Extended and signs tested Mar 15 1997 by Olivier Gérard.

STATUS

approved