... matrix.Next, given n and r ∈ {2, . . . , n}, we determine the maximum order of bases for Znwith constant cardinality r. We also give subsets o f Znwith such an order. Since weare only interested in ... havethe same order as S.Let us denote by Sn,rthe set of bases for Znthat contain 0 and have cardinality r,with 2 ≤ r ≤ n. Note that for each pair (n, r), Sn,ris nonempty. Clearly, if n ... = h ∈ A.The next result is an immediate consequence of ii) in Lemma 2.2. We denote by |M|the cardinality of the set M.Corollary 2.3 Let A ⊆ Znbe nonempty. Then |H(A)| divides |A|.Next we...