OFFSET
0,3
FORMULA
G.f.: A(x) = (1/x)*Series_Reversion(x/B(x)) where A(x/B(x)) = B(x) = Sum_{n>=0} x^n/n!^2.
a(n) = [x^n/n!^2] B(x)^(n+1)/(n+1).
EXAMPLE
G.f.: A(x) = 1 + x + 5*x^2/2!^2 + 64*x^3/3!^2 + 1577*x^4/4!^2 +...
where A(x) = Sum_{n>=0} x^n*A(x)^n/n!^2.
Also, A(x/B(x)) = B(x) = 1 + x + x^2/2!^2 + x^3/3!^2 + x^4/4!^2 +...
PROG
(PARI) {a(n)=local(B=sum(m=0, n, x^m/m!^2+O(x^(n+2)))); n!^2*polcoeff(serreverse(x/B)/x, n)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jan 04 2011
STATUS
approved