A005748 Number of n-covers of an unlabeled 7-set. (Formerly M5098)

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

Offset

1,2

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

Prog

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

Crossrefs

A diagonal of A055080.

Sequence in context: A167031 A268787 A272183 * A230236 A093144 A285393

Adjacent sequences: A005745 A005746 A005747 * A005749 A005750 A005751

Keyword

nonn

Author

N. J. A. Sloane, Simon Plouffe

Extensions

Corrected and extended by Vladeta Jovovic, Jun 13 2000

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

Status

approved