A009107 Expansion of e.g.f. cos(x)/cos(tanh(x)), even powers only.

1, 0, -8, 56, 512, -54912, 2590336, -69311488, -3936710656, 914002857984, -81770855727104, -2175764106870784, 2405710131432685568, -359158536158603378688, -106865524988327138951168

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