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A205576 E.g.f.: 1/(cos(x) - x*cosh(x)). 1
1, 1, 3, 15, 89, 685, 6331, 67851, 833265, 11509209, 176580211, 2980609863, 54883547465, 1094804661509, 23519070268331, 541334395140675, 13290451105971425, 346691343404639153, 9575683088728787683, 279175712231827548543, 8567653762387524327225 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Radius of convergence of e.g.f. is |x| < r where r = 0.6516970063076... satisfies cosh(r) = cos(r)/r.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..200

FORMULA

a(n) ~ n!/((sin(r)+cosh(r)+sinh(r)*r)*r^(n+1)), where r = 0.6516970063... is the root of the equation r*cosh(r) = cos(r). - Vaclav Kotesovec, Jun 27 2013

EXAMPLE

E.g.f.: A(x) = 1 + x + 3*x^2/2! + 15*x^3/3! + 89*x^4/4! + 685*x^5/5! +...

MATHEMATICA

CoefficientList[Series[1/(Cos[x]-x*Cosh[x]), {x, 0, 20}], x]* Range[0, 20]! (* Vaclav Kotesovec, Jun 27 2013 *)

PROG

(PARI) {a(n)=n!*polcoeff(1/(cos(x+x*O(x^n))-x*cosh(x+x*O(x^n))), n)}

CROSSREFS

Sequence in context: A231257 A074541 A074550 * A173695 A255688 A025748

Adjacent sequences:  A205573 A205574 A205575 * A205577 A205578 A205579

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jan 29 2012

STATUS

approved

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Last modified December 12 14:27 EST 2018. Contains 318075 sequences. (Running on oeis4.)