0,3

Vaclav Kotesovec, Table of n, a(n) for n = 0..350

G.f.: A(x) = 1 + x*B(x)^3 where B(x) is the g.f. of A137963.

a(n) = Sum_{k=0..n-1} C(3*(n-k),k)/(n-k) * C(5*k,n-k-1) for n>0 with a(0)=1. - Paul D. Hanna, Jun 16 2009

a(n) ~ sqrt(3*s*(1-s)*(5-6*s) / ((140*s - 120)*Pi)) / (n^(3/2) * r^n), where r = 0.1085884782751570249717333800652227343328635496829... and s = 1.301018963559115613510052458264916439485131890857... are real roots of the system of equations s = 1 + r*(1 + r*s^5)^3, 15 * r^2 * s^4 * (1 + r*s^5)^2 = 1. - Vaclav Kotesovec, Nov 22 2017

(PARI) {a(n)=local(A=1+x*O(x^n)); for(i=0, n, A=1+x*(1+x*A^5)^3); polcoeff(A, n)}

(PARI) a(n)=if(n==0, 1, sum(k=0, n-1, binomial(3*(n-k), k)/(n-k)*binomial(5*k, n-k-1))) \\ Paul D. Hanna, Jun 16 2009

Cf. A137963, A137961; A137953, A137957, A137969.

Sequence in context: A007277 A025595 A151331 * A267662 A081341 A169604

Adjacent sequences: A137959 A137960 A137961 * A137963 A137964 A137965

Paul D. Hanna, Feb 26 2008

approved