A005748 Number of n-covers of an unlabeled 7-set.

1, 20, 348, 6093, 108182, 1890123, 31500927, 490890277, 7086257602, 94548676765, 1167995082810, 13406707973018, 143598707530374, 1441525802509250, 13619352767824724, 121574625625030584, 1029031775725235400, 8285521569322196569, 63648858792893665714

Offset: 1

Author

N. J. A. Sloane, Simon Plouffe

Keywords

• nonn

Comments

Number of n X 7 binary matrices with at least one 1 in every column up to row and column permutations. - Andrew Howroyd, Feb 28 2023

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 = 1..1000
• Vladeta Jovovic, Binary matrices up to row and column permutations

Crossrefs

A diagonal of A055080.

Programs

PARI

Vec(G(7, x) - G(6, x) + O(x^30)) \\ G defined in A028657. - Andrew Howroyd, Feb 28 2023

Extensions

Corrected and extended by Vladeta Jovovic, Jun 13 2000

Terms a(17) and beyond from Andrew Howroyd, Feb 28 2023