A056885 Triangle T(n,k) = number of minimal covers of an unlabeled n-set that cover k points of that set uniquely, k=0..n.

1, 0, 1, 0, 0, 2, 0, 0, 1, 3, 0, 0, 1, 3, 5, 0, 0, 1, 5, 8, 7, 0, 0, 1, 8, 19, 17, 11, 0, 0, 1, 12, 45, 56, 35, 15, 0, 0, 1, 17, 107, 194, 151, 65, 22, 0, 0, 1, 24, 244, 713, 728, 365, 118, 30, 0, 0, 1, 32, 547, 2697, 3996, 2413, 835, 203, 42, 0, 0, 1, 42, 1173, 10356, 24446

Offset: 0

Author

Vladeta Jovovic, Sep 04 2000

Keywords

• nonn
• tabl
• nice

Comments

Row sums give A048194.

Examples

			[1], [0,1], [0,0,2], [0,0,1,3], [0,0,1,3,5], [0,0,1,5,8,7], ...; There are 21=1+5+8+7 minimal covers of an unlabeled 5-set.
		

Links

• Sean A. Irvine, Java program (github)
• V. Jovovic, Formula for T(n,k).

Crossrefs

Cf. A035347 for labeled case.