

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
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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*n1]) \\ 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



