A376791 - OEIS

%I #13 Oct 04 2024 06:16:47

%S 1,2,6,21,76,282,1065,4074,15732,61193,239406,941064,3713701,14703896,

%T 58383138,232383841,926943678,3704410890,14828984641,59450138412,

%U 238659074286,959247218253,3859777477944,15546444564846,62675854384977,252893414725842,1021208266423260

%N Expansion of 1/sqrt((1 - x^3)^2 - 4*x).

%F a(n) = Sum_{k=0..floor(n/3)} binomial(2*n-5*k,k) * binomial(2*n-6*k,n-3*k).

%o (PARI) my(N=30, x='x+O('x^N)); Vec(1/sqrt((1-x^3)^2-4*x))

%o (PARI) a(n) = sum(k=0, n\3, binomial(2*n-5*k, k)*binomial(2*n-6*k, n-3*k));

%Y Cf. A001850, A349713, A376792.

%Y Cf. A053442, A098479.

%K nonn

%O 0,2

%A _Seiichi Manyama_, Oct 04 2024