OFFSET
1,4
REFERENCES
A. Errera, Analysis situs: Un problème d'énumération, Memoires Acad. Bruxelles (1931), Serie 2, Vol. 11, No. 6, 26pp.
FORMULA
T(n,k) = 1/(2n-k) Sum( d | gcd(2n-k,n-k) = mu(d) C((2n-k)/d,(n-k)/d) ). - Wouter Meeussen, Jul 20 2008
EXAMPLE
Triangle T(n,k), 1<=k<=n, begins:
1;
1, 0;
2, 1, 0;
5, 2, 1, 0;
14, 7, 3, 1, 0;
42, 20, 9, 3, 1, 0;
132, 66, 30, 12, 4, 1, 0;
429, 212, 99, 40, 15, 4, 1, 0;
MATHEMATICA
Table[1/(2n-k) Plus@@ (MoebiusMu[ # ]Binomial[(2n-k)/#, (n-k)/# ]&/@ Divisors[GCD[2n-k, n-k]]), {n, 12}, {k, n}] (* Wouter Meeussen, Jul 20 2008 *)
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Philippe Deléham, Aug 08 2007
EXTENSIONS
Edited by N. J. A. Sloane, Oct 08 2007
STATUS
approved