OFFSET
0,7
LINKS
Amiram Eldar, Table of n, a(n) for n = 0..450
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 751.
FORMULA
E.g.f.: x^5*log(-1/(-1+x)).
Recurrence: a(1)=0, a(2)=0, a(4)=0, a(3)=0, a(5)=0, a(6)=720, (-n^2+4*n+5)*a(n) + (-4+n)*a(n+1)=0.
From Amiram Eldar, Oct 07 2020: (Start)
a(n) = n! / (n-5) for n > 5.
Sum_{n>=6} 1/a(n) = 87/8 - 4*e. (End)
Sum_{n>=6} (-1)^n/a(n) = 53/24 - 6/e. - Amiram Eldar, Aug 20 2022
MAPLE
spec := [S, {B=Cycle(Z), S=Prod(Z, Z, Z, Z, Z, B)}, labeled]: seq(combstruct[count](spec, size=n), n=0..20);
MATHEMATICA
a[n_] := If[n < 6, 0, n!/(n - 5)]; Array[a, 20, 0] (* Amiram Eldar, Oct 07 2020 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
encyclopedia(AT)pommard.inria.fr, Jan 25 2000
STATUS
approved