OFFSET
3,1
LINKS
Alois P. Heinz, Table of n, a(n) for n = 3..150
FORMULA
E.g.f.: T^3/3 where T=T(x) is Euler's tree function (see A000169).
a(n) = (n-1)*(n-2)*n^(n-3). - Vaclav Kotesovec, Oct 05 2013
a(n) = 2*A053507(n). - Vaclav Kotesovec, Oct 07 2016
EXAMPLE
a(4)=24: 1->2->3->1<-4; 2->3->1->2<-4; 3->1->2->3<-4 1->3->2->1<-4; 3->2->1->3<-4; 2->1->3->2<-4 (repeat with 1,2, then 3 excluded from cycle)
MAPLE
T := x->-LambertW(-x); a := []; f := series((T(x))^3/3, x, 24); for m from 1 to 24 do a := [op(a), op(2*m-1, f)*(m+2)! ] od; print(a);
MATHEMATICA
nn = 18; t = Sum[n^(n - 1) x^n/n!, {n, 1, nn}];
Range[0, nn]! CoefficientList[Series[2 t^3/3!, {x, 0, nn}], x] (* Geoffrey Critzer, Aug 14 2013 *)
PROG
(PARI) for(n=3, 50, print1((n-1)*(n-2)*n^(n-3), ", ")) \\ G. C. Greubel, Nov 14 2017
(Magma) [(n-1)*(n-2)*n^(n-3): n in [3..50]]; // G. C. Greubel, Nov 14 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Len Smiley, Nov 27 2001
STATUS
approved