A009044 Expansion of cos(sin(x))/cosh(x), even terms only.

1, -2, 16, -248, 6336, -244480, 13409408, -999327488, 97590304768, -12120423043072, 1867576863899648, -349745166753398784, 78248003933970006016, -20613585750577859067904, 6315933020629432945606656

Offset

0,2

Links

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

Formula

a(n) ~ (2*n)! * (-1)^n * cosh(sinh(Pi/2)) * 4^(n+1) / Pi^(2*n+1). - Vaclav Kotesovec, Jan 22 2015

Mathematica

nn = 20; Table[(CoefficientList[Series[Cos[Sin[x]]*Sech[x], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* Vaclav Kotesovec, Jan 22 2015 *)

Prog

(PARI) x='x+O('x^50); v=Vec(serlaplace(cos(sin(x))/cosh(x))); vector(#v\2, n, v[2*n-1]) \\ G. C. Greubel, Jul 23 2018

Crossrefs

Sequence in context: A012457 A138764 A009833 * A019318 A090727 A108242

Adjacent sequences: A009041 A009042 A009043 * A009045 A009046 A009047

Keyword

sign

Author

R. H. Hardin

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997

Status

approved