Abstract
We say that an optimal λ-packing ( λ-covering) of pairs with triples can be nested if it is possible to add one point to each block such that an optimal 2 λ-packing (2 λ-covering) of pairs with quadruples is obtained. A packing (covering) of order v can exist only if v ≥ 4 and v / 3 λ(v - 1) / 2 = v / 4 2λ(v - 1) / 3 ( v / 3 λ(v - 1) / 2 = v / 4 2λ (v - 1) / 3 ). It is shown in this paper that this condition is also sufficient, except possibly for v = 20.
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Shalaby, N., Yin, J. Nested Optimal λ-Packings and λ-Coverings of Pairs with Triples. Designs, Codes and Cryptography 15, 271–278 (1998). https://doi.org/10.1023/A:1008373226759
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DOI: https://doi.org/10.1023/A:1008373226759