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A279109 Denominators of coefficients in expansion of 1/(1 + cos(sqrt(x))). 3

%I

%S 2,8,48,5760,80640,14515200,958003200,1394852659200,41845579776000,

%T 25609494822912000,4865804016353280000,528941518954168320000,

%U 1240896803466478878720000,1613165844506422542336000000,609776689223427721003008000000

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

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

%H Clark Kimberling, <a href="/A279109/b279109.txt">Table of n, a(n) for n = 0..1000</a>

%F (1/2)*A279110.

%e 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.

%t z = 26; t = CoefficientList[Series[1/(1 + Cos[Sqrt[x]]), {x, 0, z}], x];

%t u = Numerator[t] (* A089171, unsigned *)

%t Denominator[t] (* A279109 *)

%Y Cf. A089171, A279110.

%K nonn,easy,frac

%O 0,1

%A _Clark Kimberling_, Dec 07 2016

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Last modified March 26 12:43 EDT 2019. Contains 321497 sequences. (Running on oeis4.)