G.f. satisfies: A(x) = (1 + x*A(x)^(p/r))^r, where p=10, r=9.
G.f.: hypergeom([9, 10, ..., 18]/10, [10, 11, ..., 18]/9, (10^10/9^9)*x).
E.g.f.: hypergeom([9, 11, 12, ..., 18]/10, [10, 11, ..., 18]/9, (10^10/9^9) * x). Cf. _Ilya Gutkovsky_ in
A118971. (End)
a(n) = binomial(10*n + 8 , n+1)/(9*n + 8) which is instance k = 9 of c(k, n+1) given in a comment in
A130564. x*A(x), with the above given g.f. A(x), is the compositional inverse of y*(1 - y)^9, hence A(x)*(1 - x*A(x))^9 = 1. For another formula for A(x) involving the hypergeometric function 9F8 see the analog formula in
A234513. -
Wolfdieter Lang, Feb 15 2024
a(n) ~ 4^(5*n+4) * 5^(10*n+17/2) / (3^(18*n+17) * n^(3/2) * sqrt(Pi)). -
Amiram Eldar, Sep 14 2025