A066019 - OEIS

%I #14 Mar 06 2020 04:03:56

%S 1,2,1,2,3,1,2,3,4,1,3,5,5,5,1,3,6,8,7,6,1,3,8,12,12,9,7,1,4,9,17,20,

%T 20,12,8,1

%N Triangle of covering numbers T(n,k) = C(n,k,k-2), n >= 3, 3 <= k <= n.

%C C(v,k,t) is the smallest number of k-subsets of an n-set such that every t-subset is contained in at least one of the k-subsets.

%D CRC Handbook of Combinatorial Designs, 1996, p. 263.

%D W. H. Mills and R. C. Mullin, Coverings and packings, pp. 371-399 of Jeffrey H. Dinitz and D. R. Stinson, editors, Contemporary Design Theory, Wiley, 1992.

%D Kari J. Nurmela and Patric R. J. Östergård, Covering t-sets with (t+2)-sets. Proceedings of the Conference on Optimal Discrete Structures and Algorithms-ODSA '97 (Rostock).

%H D. Gordon, <a href="http://www.dmgordon.org/cover">La Jolla Repository of Coverings</a>

%H Kari J. Nurmela and Patric R. J. Östergård, <a href="https://doi.org/10.1016/S0166-218X(99)00090-6">Covering t-sets with (t+2)-sets</a>, Discrete Appl. Math. 95 (1999), no. 1-3, 425-437.

%H <a href="/index/Cor#covnum">Index entries for covering numbers</a>

%e Triangle begins:

%e   1;

%e   2 1;

%e   2 3 1;

%e   2 3 4 1;

%e   3 5 5 5 1;

%e   ...

%K nonn,tabl,nice,more

%O 3,2

%A _N. J. A. Sloane_, Dec 30 2001