A162863 E.g.f. satisfies: A(x) = (1 + x*A(x)^2)^A(x).

1, 1, 6, 75, 1448, 38020, 1265454, 51069326, 2423671144, 132284727792, 8164129781280, 562204918658592, 42737232766827576, 3554783958154270608, 321149971312286643240, 31316069883727673961240

Offset

0,3

Comments

More generally, if G(x) = (1 + x*G(x)^p)^(G(x)^q), then

[x^n/n! ] G(x)^m = Sum_{k=0..n} m*(pn+qk+m)^(k-1) * Stirling1(n,k), and

[x^n/n! ] log(G(x)) = Sum_{k=1..n} (pn+qk)^(k-1) * Stirling1(n,k).

Links

G. C. Greubel, Table of n, a(n) for n = 0..338

Formula

(1) a(n) = Sum_{k=0..n} (2n+k+1)^(k-1) * Stirling1(n,k).

Let A(x)^m = Sum_{n>=0} a(n,m)*x^n/n!, then:

(2) a(n,m) = Sum_{k=0..n} m*(2n+k+m)^(k-1) * Stirling1(n,k) ;

(3) a(n,m) = Sum_{k=0..n} m*(2n+k+m)^(k-1) * {[x^(n-k)] Product_{j=1..n-1} (1-j*x)} ;

(4) a(n,m) = Sum_{k=0..n} m*(2n+k+m)^(k-1) * n!*{[x^(n-k)] (log(1+x)/x)^k/k!}.

Let log(A(x)) = Sum_{n>=0} L(n)*x^n/n!, then

(5) L(n) = Sum_{k=1..n} (2n+k)^(k-1) * Stirling1(n,k).

a(n) ~ s^2*sqrt(r*s*(1+r*s^2)/(1+r*s^2*(2+s*(6+r*s*(1+2*s))))) * n^(n-1) / (exp(n)*r^n), where r = 0.1389785143116673015... and s = 1.435128235324409145... are roots of the system of equations s*(2*r*s^2/(1+r*s^2) + log(1+r*s^2)) = 1, (1+r*s^2)^s = s. - Vaclav Kotesovec, Jul 15 2014

Example

E.g.f.: A(x) = 1 + x + 6*x^2/2! + 75*x^3/3! + 1448*x^4/4! +...
A(x)^2 = 1 + 2*x + 14*x^2/2! + 186*x^3/3! + 3712*x^4/4! +...
log(A(x)) = A(x)*log(1 + x*A(x)^2) where
log(A(x)) = x + 5*x^2/2! + 59*x^3/3! + 1106*x^4/4! + 28524*x^5/5! +...
log(1 + x*A(x)^2) = x + 3*x^2/2! + 32*x^3/3! + 570*x^4/4! + 14264*x^5/5! +...

Mathematica

Table[Sum[(2*n+k+1)^(k-1) * StirlingS1[n, k], {k, 0, n}], {n, 0, 20}] (* Vaclav Kotesovec, Jul 15 2014 *)

Prog

(PARI) {a(n, m=1)=sum(k=0, n, m*(2*n+k+m)^(k-1)*polcoeff(prod(j=1, n-1, 1-j*x), n-k))}
(PARI) {a(n, m=1)=n!*sum(k=0, n, m*(2*n+k+m)^(k-1)*polcoeff((log(1+x+x*O(x^n))/x)^k/k!, n-k))}
(PARI) {Stirling1(n, k)=n!*polcoeff(binomial(x, n), k)}
{a(n, m=1)=sum(k=0, n, m*(2*n+k+m)^(k-1)*Stirling1(n, k))}
(Magma) [(&+[(2*n+k+1)^(k-1)*StirlingFirst(n, k) : k in [0..n]]): n in [0..20]]; // G. C. Greubel, Oct 24 2018

Crossrefs

Cf. A008275 (Stirling1), variants: A162655, A141209.

Sequence in context: A234529 A139088 A193784 * A216136 A360471 A126462

Adjacent sequences: A162860 A162861 A162862 * A162864 A162865 A162866

Keyword

nonn

Author

Paul D. Hanna, Jul 15 2009

Status

approved