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A009107 Expansion of e.g.f. cos(x)/cos(tanh(x)), even powers only. 2
1, 0, -8, 56, 512, -54912, 2590336, -69311488, -3936710656, 914002857984, -81770855727104, -2175764106870784, 2405710131432685568, -359158536158603378688, -106865524988327138951168 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..242

MATHEMATICA

With[{nmax = 60}, CoefficientList[Series[Cos[x]/Cos[Tanh[x]], {x, 0, nmax}], x]*Range[0, nmax]!][[1 ;; -1 ;; 2]] (* G. C. Greubel, Jul 26 2018 *)

PROG

(PARI) x='x+O('x^50); v=Vec(serlaplace(cos(x)/cos(tanh(x)))); vector(#v\2, n, v[2*n-1]) \\ G. C. Greubel, Jul 26 2018

CROSSREFS

Cf. A009297.

Sequence in context: A086787 A218125 A098914 * A209665 A208944 A209072

Adjacent sequences:  A009104 A009105 A009106 * A009108 A009109 A009110

KEYWORD

sign

AUTHOR

R. H. Hardin

EXTENSIONS

Extended with signs by Olivier Gérard, Mar 15 1997

STATUS

approved

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Last modified December 7 17:41 EST 2019. Contains 329847 sequences. (Running on oeis4.)