A005786 Number of 6-covers of an unlabeled n-set.

1, 6, 43, 336, 2864, 25326, 223034, 1890123, 15115098, 112980937, 787320629, 5121184083, 31188412225, 178517111561, 964196387369, 4933278065881, 23997707450765, 111358094980387, 494444748602595, 2106504840061571

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn

Comments

Number of 6 X n binary matrices with at least one 1 in every column up to row and column permutations.

References

• R. J. Clarke, Covering a set by subsets, Discrete Math., 81 (1990), 147-152.
• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• Andrew Howroyd, Table of n, a(n) for n = 0..500
• Vladeta Jovovic, Binary matrices up to row and column permutations

Crossrefs

Column 6 of A055080.

Cf. A002620, A005783, A005784, A005785, A055066.

Programs

PARI

Vec(G(6, x)*(1 - x) + O(x^40)) \\ G defined in A028657. - Andrew Howroyd, Feb 28 2023

Extensions

More terms from Vladeta Jovovic, Jun 12 2000

a(0)=1 prepended by Alois P. Heinz, Aug 08 2022