A009167 - OEIS

A009167

Expansion of cosh(tan(x)/cos(x)).

1, 1, 21, 717, 38857, 3158329, 363525789, 56250039237, 11210469917713, 2783865475754737, 840008000833503141, 302092032859131150141, 127513257396264637784281, 62381091849825754078253353

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,3

LINKS

Table of n, a(n) for n=0..13.

MATHEMATICA

With[{nn=30}, Take[CoefficientList[Series[Cosh[Tan[x]/Cos[x]], {x, 0, nn}], x] Range[0, nn]!, {1, -1, 2}]] (* Harvey P. Dale, Feb 11 2015 *)

CROSSREFS

Sequence in context: A100713 A056565 A187359 * A012479 A317824 A297504

Adjacent sequences: A009164 A009165 A009166 * A009168 A009169 A009170

KEYWORD

nonn

AUTHOR

R. H. Hardin

EXTENSIONS

Extended and signs tested Mar 15 1997 by Olivier Gérard.

Previous Mathematica program replaced by Harvey P. Dale, Feb 11 2015

STATUS

approved