OFFSET
0,3
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 0..219
FORMULA
G.f. satisfies: A(x) = Sum_{n>=0} x^n * Sum_{k=0..n} Stirling2(n,k)*A(x)^k.
EXAMPLE
G.f.: A(x) = 1 + x + 3*x^2 + 11*x^3 + 46*x^4 + 210*x^5 + 1022*x^6 +...
where
A(x) = 1 + x*A(x)/(1-x) + x^2*A(x)^2/((1-x)*(1-2*x)) + x^3*A(x)^3/((1-x)*(1-2*x)*(1-3*x)) + x^4*A(x)^4/((1-x)*(1-2*x)*(1-3*x)*(1-4*x)) +...
PROG
(PARI) {a(n)=local(A=1+x); for(i=1, n, A=sum(m=0, n, x^m*A^m/prod(k=1, m, 1-k*x +x*O(x^n)) )); polcoeff(A, n)}
for(n=0, 20, print1(a(n), ", "))
(PARI) {Stirling2(n, k)=n!*polcoeff(((exp(x+x*O(x^n))-1)^k)/k!, n)}
{a(n)=local(A=1+x); for(i=0, n, A=sum(m=0, n, x^m*sum(k=0, m, Stirling2(m, k)*(A+x*O(x^n))^k))); polcoeff(A, n)}
for(n=0, 20, print1(a(n), ", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, May 04 2013
STATUS
approved