A009795 Expansion of tanh(sin(x))*sin(x).

0, 2, -16, 288, -10368, 610304, -52885504, 6324756480, -997700468736, 200677417680896, -50126593037172736, 15222954297995034624, -5523668414636262162432, 2360101997206034337234944, -1172849951576110533537955840, 670735996458876867872135577600

Offset

0,2

Links

Table of n, a(n) for n=0..15.

Formula

a(n) ~ (2*n)! * (-1)^(n+1) * 2 * Pi / (sqrt(4 + Pi^2) * (log((Pi + sqrt(4 + Pi^2))/2))^(2*n+1)). - Vaclav Kotesovec, Jan 24 2015

Mathematica

Tanh[ Sin[ x ] ]*Sin[ x ] (* Even Part *)
nn = 20; Table[(CoefficientList[Series[Sin[x]*Tanh[Sin[x]], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* Vaclav Kotesovec, Jan 24 2015 *)

Crossrefs

Sequence in context: A055546 A009549 A254744 * A182562 A112722 A223664

Adjacent sequences: A009792 A009793 A009794 * A009796 A009797 A009798

Keyword

sign

Author

R. H. Hardin

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997

Status

approved