A379281 G.f. A(x) satisfies A(x) = 1/( (1 - x) * (1 - x*A(x)) )^2.

1, 4, 18, 96, 575, 3706, 25078, 175666, 1262723, 9261018, 69024147, 521281642, 3980391050, 30678331440, 238350850248, 1864751821958, 14678131286357, 116160233811868, 923684828888152, 7376541052964806, 59137050311947284, 475757909357776656, 3839678158239147611

Offset: 0

Author

Seiichi Manyama, Dec 19 2024

Keywords

• nonn

Crossrefs

Cf. A379282, A379283.

Cf. A199475.

Programs

PARI

a(n) = 2*sum(k=0, n, binomial(2*n-k+2, k)*binomial(3*n-3*k+1, n-k)/(2*n-k+2));

Formula

G.f.: B(x)^2 where B(x) is the g.f. of A199475.

a(n) = 2 * Sum_{k=0..n} binomial(2*n-k+2,k) * binomial(3*n-3*k+1,n-k)/(2*n-k+2).