|
|
A216534
|
|
Number of cycles in all partial functions on {1,2,...,n}.
|
|
1
|
|
|
0, 1, 7, 62, 696, 9564, 156115, 2957072, 63822024, 1547005920, 41624943383, 1231358443776, 39728327494064, 1388514386058240, 52264389341358675, 2108028274231109632, 90708364554174003184, 4147927057963872055296, 200876745049904503019271, 10270802025081264529408000, 552906921706607979733097736
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,3
|
|
LINKS
|
|
|
FORMULA
|
E.g.f.: exp(T(x))*log(1/(1-T(x)))/(1-T(x)), where T(x) is the e.g.f. for A000169.
a(n) ~ exp(1)/2 * n^n * log(n) * (1 + (gamma+log(2))/log(n) - 2*sqrt(2*Pi)/(3*sqrt(n)*log(n))), where gamma is Euler-Mascheroni constant (A001620). - Vaclav Kotesovec, Sep 30 2013
|
|
MAPLE
|
T:= -LambertW(-x):
a:= n-> n! *coeff(series(exp(T)*log(1/(1-T))/(1-T), x, n+1), x, n):
|
|
MATHEMATICA
|
nn=20; t=Sum[n^(n-1)x^n/n!, {n, 1, nn}]; a=Exp[t]/(1-t)^y; b=D[a, y]/.y->1; Range[0, nn]!CoefficientList[Series[b, {x, 0, nn}], x]
CoefficientList[Series[Log[1+LambertW[-x]]/(x*(1+1/LambertW[-x])), {x, 0, 20}], x]* Range[0, 20]! (* Vaclav Kotesovec, Sep 30 2013 *)
|
|
PROG
|
(PARI) x='x+O('x^30); concat([0], Vec(serlaplace( log(1+lambertw(-x))/( x*(1+ 1/lambertw(-x))) ))) \\ G. C. Greubel, Sep 04 2018
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|