OFFSET
0,5
LINKS
G. A. Kamel, Partial Chain Topologies on Finite Sets, Computational and Applied Mathematics Journal. Vol. 1, No. 4, 2015, pp. 174-179.
MAPLE
g:=(r, n)->(n!/r!)*add(1/k!, k=1..n-r);
g2:=r->[seq(g(r, n), n=0..30)];
g2(3);
PROG
(PARI) a(n) = (n!/3!)*sum(k=1, n-3, 1/k!); \\ Michel Marcus, Jan 30 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jan 30 2016
STATUS
approved