A279109 Denominators of coefficients in expansion of 1/(1 + cos(sqrt(x))).

2, 8, 48, 5760, 80640, 14515200, 958003200, 1394852659200, 41845579776000, 25609494822912000, 4865804016353280000, 528941518954168320000, 1240896803466478878720000, 1613165844506422542336000000, 609776689223427721003008000000

Offset

0,1

Comments

The numerators are the absolute values of the numbers at A089171.

Links

Clark Kimberling, Table of n, a(n) for n = 0..1000

Formula

(1/2)*A279110.

Example

1/2 + (1/8)x + (1/48)x^2 + (17/5760)x^3 + ... ; 1/2, 1/8, 1/48, 17/5760, 31/80640, ... = |A089171|/A279109.

Mathematica

z = 26; t = CoefficientList[Series[1/(1 + Cos[Sqrt[x]]), {x, 0, z}], x];
u = Numerator[t] (* A089171, unsigned *)
Denominator[t]   (* A279109 *)

Crossrefs

Cf. A089171, A279110.

Sequence in context: A009751 A356658 A279239 * A355667 A366239 A364592

Adjacent sequences: A279106 A279107 A279108 * A279110 A279111 A279112

Keyword

nonn,easy,frac

Author

Clark Kimberling, Dec 07 2016

Status

approved