OFFSET
0,4
COMMENTS
This is essentially the same sequence as A014623. - N. J. A. Sloane, Jul 24 2022
Compare the definition of e.g.f. A(x) to the trivial statement:
if F(x) = 1 + Series_Reversion( Integral F(-x)^2 dx ) then F(x) = 1/(1-x).
FORMULA
E.g.f. satisfies: A(x) = 1 + Integral 1/A(1 - A(x)) dx. - Paul D. Hanna, Jul 10 2015
EXAMPLE
E.g.f: A(x) = 1 + x + x^2/2! + 2*x^3/3! + 7*x^4/4! + 33*x^5/5! +...
Let I(x) = Series_Reversion(A(x) - 1) = Integral A(-x) dx then
I(x) = x - x^2/2! + x^3/3! - 2*x^4/4! + 7*x^5/5! - 33*x^6/6! +...
PROG
(PARI) {a(n)=local(A=1+x+x*O(x^n)); for(i=0, n, A=1+serreverse(intformal(subst(A, x, -x)^1))); n!*polcoeff(A, n)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Sep 07 2008
STATUS
approved