OFFSET
0,3
EXAMPLE
G.f.: A(x) = 1 + x + 2*x^2 + 8*x^3 + 44*x^4 + 305*x^5 + 2521*x^6 +...
where the g.f. satisfies:
A(x) = 1 + x*A(x) + x^2*A(x)^5 + x^3*A(x)^15 + x^4*A(x)^35 + x^5*A(x)^70 + x^6*A(x)^126 + x^7*A(x)^210 +...+ x^n*A(x)^(n*(n+1)*(n+2)*(n+3)/4!) +...
PROG
(PARI) {a(n)=local(A=1+x); for(i=1, n, A=1+sum(m=1, n, x^m*(A+x*O(x^n))^binomial(m+3, 4))); polcoeff(A, n)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jun 16 2011
STATUS
approved