OFFSET
0,3
EXAMPLE
G.f.: A(x) = 1 + x + 3*x^2 + 19*x^3 + 235*x^4 + 5611*x^5 + 261387*x^6 + ...
where
A(x) = 1 + x*A(2*x) + x^2*A(2*x)*A(4*x) + x^3*A(2*x)*A(4*x)*A(8*x) + ...
PROG
(PARI) {a(n, r=1)=local(A=1+x); for(i=1, n, A=1+sum(m=1, n, r^m*x^m*prod(k=1, m, subst(A, x, 2^k*x+x*O(x^n))))); polcoeff(A, n)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Oct 15 2013
STATUS
approved