%I #4 Dec 12 2016 09:17:06
%S 1,1,2,2,24,24,720,720,4480,40320,3628800,3628800,479001600,95800320,
%T 2641766400,87178291200,1902071808000,20922789888000,6402373705728000,
%U 6402373705728000,810967336058880000,143111882833920000,66117689869271040000,13223537973854208000
%N Denominators of coefficients in expansion of (cos x)/(1 - x - x^2).
%H Clark Kimberling, <a href="/A279311/b279311.txt">Table of n, a(n) for n = 0..1000</a>
%e (1/1) + (1/1)x + (3/2)x^2 + (5/2)x^3 + ... ; 1/1, 1/1, 3/2, 5/2, ... = A279310/A279311.
%t z = 30; t = CoefficientList[Series[Cos[x]/(1 - x - x^2), {x, 0, z}], x];
%t Numerator[t] (* A279310 *)
%t Denominator[t] (* A279311 *)
%Y Cf. A279310.
%K nonn,easy,frac
%O 0,3
%A _Clark Kimberling_, Dec 11 2016