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Dr Roy H Ogawa

Let Z = integers,
For any integer k > 0, Zk is the k dimensional product space consisting of z = (z1,   .   .   .   zk)
where the zi are in Z.
For any integer r ≥ 0, D(k,r) = { z in Zk : for each i, zi ≥ 0, & Σi=1k zi = r }