OFFSET
0,3
FORMULA
G.f. satisfies: A(x) = 1 + A(x)^2*Series_Reversion[x/A(x)^2].
G.f. satisfies: A( (x-x^2)/A(x-x^2)^2 ) = 1/(1-x).
G.f. satisfies: A( (x/(1+x)^2)/A(x/(1+x)^2)^2 ) = 1 + x.
EXAMPLE
G.f.: A(x) = 1 + x + 4*x^2 + 26*x^3 + 226*x^4 + 2395*x^5 +...
A(x/A(x)^2) = 1 + x + 2*x^2 + 5*x^3 + 14*x^4 + 42*x^5 + 132*x^6 +...
PROG
(PARI) {a(n)=local(A=1+x, F=sum(k=0, n, binomial(2*k+1, k)/(2*k+1)*x^k)+x*O(x^n)); for(i=0, n, A=subst(F, x, serreverse(x/(A+x*O(x^n))^2))); polcoeff(A, n)}
(PARI) {a(n)=local(A=1+x); for(i=1, n, A=1+A^2*serreverse(x/(A+x*O(x^n))^2)); polcoeff(A, n)}
for(n=0, 25, print1(a(n), ", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Dec 06 2009
STATUS
approved