A009080 Expansion of e.g.f. cos(x*tan(x)), even terms only.

1, 0, -12, -240, -5936, -155520, -65472, 981903104, 223580862720, 46255608778752, 10060678641587200, 2368138744630923264, 601490101481648443392, 161192778898870464512000, 43208403753541588946141184

Offset

0,3

Links

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

Example

cos(x*tan(x)) = 1/0! +0*x^2/2! -12*x^4/4! -240*x^6/6! -5936*x^8/8! -...

Mathematica

With[{nmax = 60}, CoefficientList[Series[Cos[x*Tan[x]], {x, 0, nmax}], x]*Range[0, nmax]!][[1 ;; -1 ;; 2]] (* G. C. Greubel, Jul 24 2018 *)

Prog

(PARI) x='x+O('x^60); v=Vec(serlaplace(cos(x*tan(x)))); vector(#v\2, n, v[2*n-1]) \\ G. C. Greubel, Jul 24 2018

Crossrefs

Sequence in context: A012538 A006588 A009150 * A002166 A034910 A332958

Adjacent sequences: A009077 A009078 A009079 * A009081 A009082 A009083

Keyword

sign

Author

R. H. Hardin

Extensions

Extended with signs by Olivier Gérard, Mar 15 1997

Status

approved