A011982 Covering numbers C(n,7,3).

1, 4, 4, 6, 8, 11, 13, 15, 15

Offset

7,2

Comments

a(16) <= 25.

Note that Gordon et al. (1995) as well as CRC Handbook of Combinatorial Designs give the incorrect value a(14) = 14. Daniel Gordon (private correspondence) confirmed a(14) = 15 (found by Stanisław Radziszowski in 1996); see link "Improved Lower Bounds", where it says "C(14,7,3) = 15". - Pontus von Brömssen, Feb 12 2026

References

CRC Handbook of Combinatorial Designs, 1996, p. 262.

Links

Table of n, a(n) for n=7..15.

D. Gordon, Improved Lower Bounds.

D. Gordon, La Jolla Repository of Coverings.

Daniel M. Gordon, Greg Kuperberg, and Oren Patashnik, New constructions for covering designs, Journal of Combinatorial Designs 3 (1995), Issue 4, 269-284; arXiv:math/9502238 [math.CO], 1995.

Wikipedia, Covering design.

Index entries for covering numbers.

Crossrefs

Sequence in context: A105790 A338895 A090682 * A282939 A175216 A053639

Adjacent sequences: A011979 A011980 A011981 * A011983 A011984 A011985

Keyword

nonn,hard,more

Author

N. J. A. Sloane

Extensions

a(14) corrected by Pontus von Brömssen, Feb 11 2026

Status

approved