OFFSET
0,3
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 0..378
FORMULA
G.f. satisfies: A(x) = 1 + x*[d/dx x*A(x)^3]/A(x).
a(n) ~ n! * 3^(n+1) / (Pi*exp(1)). - Vaclav Kotesovec, Aug 24 2017
a(0) = 1; a(n) = Sum_{k=0..n-1} (3*k+1) * a(k) * a(n-k-1). - Ilya Gutkovskiy, Sep 05 2024
EXAMPLE
G.f.: A(x) = 1 + x + 5*x^2 + 44*x^3 + 539*x^4 + 8337*x^5 + 154632*x^6 +...
Related expansions:
A(x)^2 = 1 + 2*x + 11*x^2 + 98*x^3 + 1191*x^4 + 18192*x^5 + 333264*x^6 +...
A'(x)*A(x) = 1 + 11*x + 147*x^2 + 2382*x^3 + 45480*x^4 + 999792*x^5 +...
where A(x) = 1 + x*A(x)^2 + 3*x^2*A'(x)*A(x).
PROG
(PARI) {a(n)=local(A=1+x); for(i=1, n, A=1+x*deriv(x*A^3)/(A+x*O(x^n))); polcoeff(A, n)}
for(n=0, 30, print1(a(n), ", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Mar 09 2013
STATUS
approved