A159310 G.f.: Product_{n>=1} (1 + a(n)*x^n/n!) = Sum_{n>=0} (n+1)^(n-1)*x^n/n! = LambertW(-x)/(-x).

1, 3, 7, 97, 601, 7576, 116929, 2482537, 42814321, 1040362966, 25933795801, 760154969850, 23297606120881, 816970034324900, 29137514248718373, 1194044411689941241, 48661170952876980481, 2227962859999303395766

Offset

1,2

Links

Table of n, a(n) for n=1..18.

Formula

G.f.: Sum_{n>=1} log(1 + a(n)*x^n/n!) = Sum_{n>=1} n^(n-1)*x^n/n! = -LambertW(-x).

G.f.: Sum_{n>=1} log(1 + a(n)*exp(-n*x)*x^n/n!) = x.

From Paul D. Hanna, Apr 15 2009: (Start)

G.f.: Sum_{n>=1} n*a(n)*x^n/(n! + a(n)*x^n) = Sum_{n>=1} n^n*x^n/n!.

G.f.: Sum_{n>=1} n*a(n)*x^n/(n!*exp(nx) + a(n)*x^n) = x/(1-x).

Recurrence:

a(n) = n^(n-1) + (n-1)!*((-1)^n + Sum_{d|n, 1<d<n} d*( -a(d)/d! )^(n/d) ) for n > 1 with a(1)=1.

(End)

Example

G.f.: W(x) = (1+x)*(1+3*x^2/2!)*(1+7*x^3/3!)*(1+97*x^4/4!)*(1+601*x^5/5!)* ...
W(x) = 1 + x + 3*x^2/2! + 4^2*x^3/3! + 5^3*x^4/4! + 6^4*x^5/5! + ...
where W(x/exp(x)) = exp(x) and exp(x*W(x)) = W(x) = LambertW(-x)/(-x).

Prog

(PARI) {a(n)=if(n<1, 0, polcoeff(sum(k=0, n, (k+1)^(k-1)*x^k/k!)/prod(k=1, n-1, 1+a(k)*x^k +x*O(x^n)), n))}
(PARI) {a(n)=if(n<1, 0, if(n==1, 1, n^(n-1) + (n-1)!*((-1)^n + sumdiv(n, d, if(d<n&d>1, d*(-a(d)/d!)^(n/d))))))} \\ Paul D. Hanna, Apr 15 2009

Crossrefs

Cf. A137852.

Sequence in context: A088419 A062592 A074349 * A362682 A299377 A129660

Adjacent sequences: A159307 A159308 A159309 * A159311 A159312 A159313

Keyword

nonn

Author

Paul D. Hanna, Apr 15 2009

Status

approved