OFFSET
1,3
LINKS
R. J. Clarke, Covering a set by subsets, Discrete Math., 81 (1990), 147-152.
FORMULA
T(n,k) = A035348(n,k)*k!, the order in which we cover the n-set is considered. - Geoffrey Critzer, Jun 28 2013
EXAMPLE
Triangle starts
1;
1, 2;
1, 12, 6;
1, 50, 132, 24;
...
MATHEMATICA
t[n_, k_] := Sum[ (-1)^i*Binomial[k, i]*(2^k - 1 - i)^n, {i, 0, k}]; Flatten[ Join[{1}, Table[t[n, k], {n, 1, 9}, {k, 1, n}]]] (* Jean-François Alcover, Dec 12 2011, after Michael Somos *)
PROG
(PARI) {T(n, k)=sum(i=0, k, (-1)^i*binomial(k, i)*(2^k-1-i)^n)} /* Michael Somos, Oct 16 2006 */
CROSSREFS
KEYWORD
AUTHOR
STATUS
approved