A009110 Expansion of e.g.f. cos(x)/cosh(tan(x)), even powers only.

1, -2, 4, 32, 400, -3680, -719168, -45313024, -1201882880, 190738937344, 41876315935744, 3729103532367872, -442609357053390848, -294584246423093633024, -75554765797484141625344, -7698772402123265223688192, 3712165683571701387680088064

Offset

0,2

Links

G. C. Greubel, Table of n, a(n) for n = 0..243

Mathematica

With[{nn=40}, Take[CoefficientList[Series[Cos[x]/Cosh[Tan[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, May 06 2016 *)

Prog

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

Crossrefs

Sequence in context: A085055 A075070 A144937 * A225170 A134958 A101460

Adjacent sequences: A009107 A009108 A009109 * A009111 A009112 A009113

Keyword

sign

Author

R. H. Hardin

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997

More terms from and prior Mathematica program replaced by Harvey P. Dale, May 06 2016

Status

approved