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A009089 Expansion of e.g.f. cos(tanh(x))/cos(x), even powers only. 1
1, 0, 8, -56, 3968, -133248, 13993088, -1139191808, 178943504384, -26439024316416, 5943319707680768, -1368130407134953472, 421233393478948782080, -137934416762714295631872, 56032481949750675250085888 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..239

MAPLE

seq(coeff(series(factorial(n)*cos(tanh(x))/cos(x), x, n+1), x, n), n=0..30, 2); # Muniru A Asiru, Jul 25 2018

MATHEMATICA

With[{nn=30}, Take[CoefficientList[Series[Cos[Tanh[x]]/Cos[x], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Jul 14 2018 *)

PROG

(PARI) x='x+O('x^50); v=Vec(serlaplace(cos(tanh(x))/cos(x))); vector(#v\2, n, v[2*n-1]) \\ G. C. Greubel, Jul 25 2018

CROSSREFS

Sequence in context: A326239 A154411 A105850 * A296466 A202863 A244958

Adjacent sequences:  A009086 A009087 A009088 * A009090 A009091 A009092

KEYWORD

sign

AUTHOR

R. H. Hardin

EXTENSIONS

Extended with signs by Olivier Gérard, Mar 15 1997

Prior Mathematica program replaced by Harvey P. Dale, Jul 14 2018

STATUS

approved

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Last modified January 17 22:33 EST 2022. Contains 350410 sequences. (Running on oeis4.)