A279110 -id:A279110 - cp's OEIS frontend

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

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Clark Kimberling, Dec 07 2016

nonn
easy
frac

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

			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.

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

Cf. A089171, A279110.

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

(1/2)*A279110.

cp's OEIS Frontend

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

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