A009680 - OEIS

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A009680

E.g.f. tan(sinh(x))*cos(x) (odd powers only).

1, 0, 12, 336, 15760, 1144704, 117385920, 16206548736, 2897776619776, 651455951990784, 179856295521635328, 59822762558026321920, 23594335379577078059008, 10887666560228980302446592

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OFFSET

1,3

LINKS

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

FORMULA

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

MATHEMATICA

With[{nn=30}, Take[CoefficientList[Series[Tan[Sinh[x]]*Cos[x], {x, 0, nn}], x]Range[0, nn-1]!, {2, -1, 2}]] (* Harvey P. Dale, Apr 01 2012 *)

CROSSREFS

Sequence in context: A368771 A009530 A159363 * A218820 A231520 A305108

Adjacent sequences: A009677 A009678 A009679 * A009681 A009682 A009683

KEYWORD

nonn

AUTHOR

R. H. Hardin

EXTENSIONS

Extended and signs tested Mar 15 1997 by Olivier Gérard.

Changed offset by Vaclav Kotesovec, Jan 24 2015

STATUS

approved