OFFSET
0,3
COMMENTS
In general, if g.f. satisfies A(x) = 1 + x*(1 + x*A(x)^p)^q, p >= 1, q >= 1, p + q > 2, then a(n) ~ sqrt(q*s*(1-s)*(p*(1-s)-s) / (2*Pi*p*(q-s-p*q*(1-s)))) / (n^(3/2) * r^n), where r and s are real roots of the system of equations s = 1 + r*(1 + r*s^p)^q, p*q * r^2 * s^(p-1) * (1 + r*s^p)^(q-1) = 1. - Vaclav Kotesovec, Nov 22 2017
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 0..300
FORMULA
G.f.: A(x) = 1 + x*B(x)^6 where B(x) is the g.f. of A137973.
a(n) = Sum_{k=0..n-1} C(6*(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(6*s*(1-s)*(5-6*s) / ((290*s - 240)*Pi)) / (n^(3/2) * r^n), where r = 0.0739607593319208338998816978154858830062403258604... and s = 1.234938729532398384561936758596402363403570701060... are real roots of the system of equations s = 1 + r*(1 + r*s^5)^6, 30 * r^2 * s^4 * (1 + r*s^5)^5 = 1. - Vaclav Kotesovec, Nov 22 2017
PROG
(PARI) {a(n)=local(A=1+x*O(x^n)); for(i=0, n, A=1+x*(1+x*A^5)^6); polcoeff(A, n)}
(PARI) a(n)=if(n==0, 1, sum(k=0, n-1, binomial(6*(n-k), k)/(n-k)*binomial(5*k, n-k-1))) \\ Paul D. Hanna, Jun 16 2009
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Feb 26 2008
STATUS
approved