OFFSET
0,2
FORMULA
G.f.: A(x) = 1/(1 - (2/3)*x*Sum_{k>=0} (k+3)!*x^k ).
EXAMPLE
A(x) = (1 + 4*x + 32*x^2 + 272*x^3 + 2400*x^4 + 21792*x^5 +..)
= 1/(1 - 4/3!*x*(3! + 4!*x + 5!*x^2 + 6!*x^3 + 7!*x^4 +..) ).
PROG
(PARI) {a(n)=local(y=4, x=X+X*O(X^n)); polcoeff(1/(1 - y/(y-1)!*x*sum(k=0, n, (y-1+k)!*x^k)), n, X)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Philippe Deléham and Paul D. Hanna, Oct 26 2005
STATUS
approved