We will first prove that the seven elements of Mk as stated in Theorem 2.2 have
distinct p-digit sums modulo 7. It suffices to show that the set M has this same
property, and this can be routinely checked from the prime factors of the elements
m 2 M given in Table 1. Note that m = 1 is not included in the table, about which
by convention we shall agree that Sp(1) = 0.