A009683 Expansion of tan(sinh(x))*x.

0, 2, 12, 222, 8120, 478810, 41517828, 4965965942, 783389808112, 157572900435762, 39359784790117500, 11953192658425797262, 4337232551752795660968, 1853172813592086586350218

Offset

0,2

Links

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

Formula

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

Mathematica

Tan[ Sinh[ x ] ]*x (* Even Part *)
nn = 20; Table[(CoefficientList[Series[x*Tan[Sinh[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: A374871 A092124 A009525 * A132879 A377642 A348332

Adjacent sequences: A009680 A009681 A009682 * A009684 A009685 A009686

Keyword

nonn

Author

R. H. Hardin

Extensions

Extended and signs tested Mar 15 1997 by Olivier Gérard.

Status

approved