OFFSET
0,2
COMMENTS
Compare to e.g.f. W(x) = LambertW(-x)/(-x) of A000272 (with offset) generated by: W(x) = exp(-1)*Sum_{n>=0} (1+x*W(x))^n/n! = Sum_{n>=0} (n+1)^(n-1)*x^n/n!.
FORMULA
E.g.f.: A(x) = Series_Reversion(x/G(x))/x, where G(x) = A(x/G(x)) = e.g.f. of A014507.
EXAMPLE
E.g.f.: A(x) = 1 + 2*x + 21*x^2/2! + 444*x^3/3! + 14415*x^4/4! +...
where A(x) = G(x*A(x)) and A(x/G(x)) = G(x) = e.g.f. of A014507:
G(x) = 1 + 2*x + 13*x^2/2! + 162*x^3/3! + 3075*x^4/4! + 80978*x^5/5! +...
PROG
(PARI) /* A(x) = 1/e*Sum_{n>=0}(1+x*A(x))^(n^2)/n! (requires precision): */
{a(n)=local(A=1+x); for(i=1, n, A=exp(-1)*sum(m=0, 3*n+10, (1+x*A +x*O(x^n))^(m^2)/m!)); polcoeff(round(serlaplace(A+x*O(x^n))), n)}
(PARI) /* E.g.f. Series_Reversion(x/G(x))/x; G(x) = e.g.f. of A014507: */
{Stirling1(n, k)=n!*polcoeff(binomial(x, n), k)}
{Bell(n)=n!*polcoeff(exp(exp(x+x*O(x^n))-1), n)}
{A014507(n)=sum(k=0, n, Stirling1(n, k)*Bell(2*k))}
{a(n)=local(G=sum(m=0, n, A014507(m)*x^m/m!)+x*O(x^n)); n!*polcoeff(serreverse(x/G)/x, n)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jul 14 2011
STATUS
approved