A009797 Expansion of tanh(sin(x))/cos(x) (odd powers only).

1, 0, 32, -336, 31744, -1588224, 207515648, -24843657216, 4860991111168, -1034712438669312, 295553381961826304, -96277515461273321472, 38465285132060037480448, -17609621553067367199670272

Offset

1,3

Links

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

Formula

a(n) ~ (2*n-1)! * (-1)^(n+1) * 8 / ((4 + Pi^2) * (log((Pi + sqrt(4 + Pi^2))/2))^(2*n)). - Vaclav Kotesovec, Jan 24 2015

Mathematica

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

Crossrefs

Sequence in context: A248068 A248069 A145402 * A240293 A254953 A335612

Adjacent sequences: A009794 A009795 A009796 * A009798 A009799 A009800

Keyword

sign

Author

R. H. Hardin

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997

Changed offset by Vaclav Kotesovec, Jan 24 2015

Status

approved