A153393 G.f.: A(x) = F(x*G(x)^2)^2 where F(x) = G(x*F(x)) = 1 + x*F(x)^3 is the g.f. of A001764 and G(x) = F(x/G(x)) = 1 + x*G(x)^2 is the g.f. of A000108 (Catalan).

1, 2, 11, 68, 449, 3102, 22167, 162626, 1218411, 9285888, 71778489, 561453704, 4436120129, 35354290118, 283876985742, 2294347190142, 18650560232199, 152386763938940, 1250801705584643, 10308949444236522, 85281112255921359

Offset: 0

Author

Paul D. Hanna, Jan 15 2009

Keywords

• nonn

Examples

			G.f.: A(x) = F(x*G(x)^2)^2 = 1 + 2*x + 11*x^2 + 68*x^3 + 449*x^4 +... where
F(x) = 1 + x + 3*x^2 + 12*x^3 + 55*x^4 + 273*x^5 + 1428*x^6 +...
F(x)^2 = 1 + 2*x + 7*x^2 + 30*x^3 + 143*x^4 + 728*x^5 + 3876*x^6 +...
F(x)^3 = 1 + 3*x + 12*x^2 + 55*x^3 + 273*x^4 + 1428*x^5 +...
G(x) = 1 + x + 2*x^2 + 5*x^3 + 14*x^4 + 42*x^5 + 132*x^6 +...
G(x)^2 = 1 + 2*x + 5*x^2 + 14*x^3 + 42*x^4 + 132*x^5 + 429*x^6 +...
		

Crossrefs

Cf. A000108, A001764; A153392, A153394.

Programs

PARI

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

Formula

a(n) = Sum_{k=0..n} C(3k+2,k)*2/(3k+2) * C(2n,n-k)*k/n for n>0 with a(0)=1.

G.f. satisfies: A(x*F(x)) = F(F(x)-1)^2 where F(x) is the g.f. of A001764.