A009554 Expansion of e.g.f. sin(x)/cos(sinh(x)) (odd powers only).

1, 2, 36, 944, 45136, 3263072, 334656960, 46199442176, 8260388524288, 1857027989588480, 512693973356712960, 170529221696594702336, 67257392621575577522176, 31036094843772953163063296

Offset

1,2

Links

G. C. Greubel, Table of n, a(n) for n = 1..233

Formula

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

Mathematica

With[{nn=30}, Take[CoefficientList[Series[Sin[x]/Cos[Sinh[x]], {x, 0, nn}], x]Range[0, nn-1]!, {2, -1, 2}]] (* Harvey P. Dale, Jan 19 2012 *)

Prog

(PARI) x='x+O('x^50); v=Vec(serlaplace(sin(x)/cos(sinh(x)))); vector((#v-1)\2 , n, v[2*n-1]) \\ G. C. Greubel, Jan 20 2018

Crossrefs

Sequence in context: A166473 A279575 A009539 * A209036 A375839 A305596

Adjacent sequences: A009551 A009552 A009553 * A009555 A009556 A009557

Keyword

nonn

Author

R. H. Hardin

Extensions

Extended and signs tested by Olivier Gérard, Mar 15 1997

Offset corrected by Vaclav Kotesovec, Jan 23 2015

Status

approved