A009095 Expansion of e.g.f. cos(tanh(x)/cos(x)), even powers only.

1, -1, -3, -117, -903, -111529, 687093, -320199453, 44530596081, -254346923089, 2006766293627373, 141849542553657147, 144420752722329270633, 17706925736601628695047, 16789499049770600380859877

Offset

0,3

Links

G. C. Greubel, Table of n, a(n) for n = 0..240

Mathematica

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

Prog

(PARI) x='x+O('x^60); v=Vec(serlaplace(cos(tanh(x)/cos(x)))); vector(#v\2, n, v[2*n-1]) \\ G. C. Greubel, Jul 26 2018

Crossrefs

Sequence in context: A267897 A132304 A097642 * A326995 A155209 A037117

Adjacent sequences: A009092 A009093 A009094 * A009096 A009097 A009098

Keyword

sign

Author

R. H. Hardin

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997

Status

approved