OFFSET
0,3
EXAMPLE
A(x) = 1 + x + 2*x^2 + 4*x^3 + 9*x^4 + 24*x^5 + 77*x^6 + 295*x^7 +...
A(x) = 1 + x*F_1(x) + x^2*F_1(x)*F_2(x) + x^3*F_1(x)*F_2(x)*F_3(x) +...
where F_n(x) = Sum_{k>=0} C(n*k,k)/((n-1)*k + 1)*x^k:
F_1(x) = 1/(1-x);
F_2(x) = 1 + x + 2x^2 + 5x^3 + 14x^4 + 42x^5 + +... (A000108);
F_3(x) = 1 + x + 3x^2 + 12x^3 + 55x^4 + 273x^5 + ...(A001764);
F_4(x) = 1 + x + 4x^2 + 22x^3 + 140x^4 + 969x^5 +...(A002293); ...
PROG
(PARI) {a(n)=local(A=1+x+x*O(x^n)); for(k=0, n, A=1+x*A* Ser(vector(n+1, i, binomial((n-k+1)*(i-1), i-1)/((n-k)*(i-1)+1)))); polcoeff(A, n) }
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jul 03 2007
STATUS
approved