A259606 G.f. satisfies: A(x) = Series_Reversion( x - A'(x)*A(x)^2 ).

1, 1, 6, 60, 790, 12488, 226176, 4567245, 101057170, 2421311002, 62292579316, 1709994461396, 49844902545256, 1536870296603860, 49965056185462360, 1708221871912841430, 61272046476315041664, 2301058164207089144028, 90309756129843950212480, 3697832634432220792202296

Offset

1,3

Links

Vaclav Kotesovec, Table of n, a(n) for n = 1..300

Formula

G.f. satisfies:

(1) A(x) = x + A'(A(x)) * A(A(x))^2.

(2) A(x) = x + Sum_{n>=1} d^(n-1)/dx^(n-1) A'(x)^n * A(x)^(2*n) / n!.

(3) A(x) = x*exp( Sum_{n>=1} d^(n-1)/dx^(n-1) A'(x)^n * A(x)^(2*n) / (n!*x) ).

a(n) ~ c * n! * n^(alfa) / LambertW(1)^n, where alfa = 2.750027682144251700567... and c = 0.005275216890926771261... - Vaclav Kotesovec, Aug 25 2017

alfa = 5*LambertW(1) - 2 + 3/(1 + LambertW(1)). - Vaclav Kotesovec, Mar 13 2023

Example

G.f.: A(x) = x + x^2 + 6*x^3 + 60*x^4 + 790*x^5 + 12488*x^6 + 226176*x^7 +...
where
A(x - A'(x)*A(x)^2) = x.

Mathematica

a[n_] := Module[{A = x}, Do[A = InverseSeries[x - D[A, x] A^2 + x O[x]^n, x], {n}]; SeriesCoefficient[A, {x, 0, n}]];
Array[a, 25] (* Jean-François Alcover, Sep 28 2020, after PARI *)

Prog

(PARI) {a(n) = local(A=x); for(i=1, n, A=serreverse(x - A^2*A' +x*O(x^n))); polcoeff(A, n)}
for(n=1, 25, print1(a(n), ", "))
(PARI) {Dx(n, F)=local(D=F); for(i=1, n, D=deriv(D)); D}
{a(n)=local(A=x, B=x^2); for(i=1, n, A = x + sum(m=1, n, Dx(m-1, (A')^m*A^(2*m)/m!)) +O(x^(n+1))); polcoeff(A, n)}
for(n=1, 25, print1(a(n), ", "))
(PARI) {Dx(n, F)=local(D=F); for(i=1, n, D=deriv(D)); D}
{a(n)=local(A=x, B=x^2); for(i=1, n, B=intformal(2*A); A = x*exp(sum(m=1, n, Dx(m-1, (A')^m*A^(2*m)/(m!*x))) +O(x^(n+1)))); polcoeff(A, n)}
for(n=1, 25, print1(a(n), ", "))

Crossrefs

Cf. A360578.

Sequence in context: A126779 A218441 A120973 * A302102 A168478 A101470

Adjacent sequences: A259603 A259604 A259605 * A259607 A259608 A259609

Keyword

nonn

Author

Paul D. Hanna, Jul 02 2015

Status

approved