OFFSET
0,4
COMMENTS
(n-1) divides a(n) for n>1.
LINKS
Eric Weisstein, q-Factorial from MathWorld.
FORMULA
E.g.f. A(x) special values: A(-1)= 0; radius of convergence = 1.
EXAMPLE
E.g.f.: A(x) = 1 + x + x^2/2! + 4*x^3/3! + 9*x^4/4! + 56*x^5/5! +...
A(x) = 1 + x + x^2*faq(2,x)/2! + x^3*faq(3,x)/3! + x^4*faq(4,x)/4! +...
A(x) = 1 + x + x^2*(1+x)/2! + x^3*(1+x)(1+x+x^2)/3! + x^4*(1+x)(1+x+x^2)(1+x+x^2+x^3)/4! +...
The q-factorial of n is faq(n,q) = Product_{k=1..n} (q^k-1)/(q-1):
faq(0,q)=1, faq(1,q)=1, faq(2,q)=(1+q), faq(3,q)=(1+q)*(1+q+q^2), faq(4,q)=(1+q)*(1+q+q^2)*(1+q+q^2+q^3), ...
PROG
(PARI) {a(n)=local(A=sum(k=0, n, x^k/k!*prod(j=1, k, (x^j-1)/(x-1)))); n!*polcoeff(A, n)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Dec 02 2008
STATUS
approved