This is confirmed by the results in Table 7, which shows the residues modulo
5 of the powers of the integers a multiple of 3, i.e., (3i)m mod 5. This table
shows that for i = 0 or 2 modulo 5, the period is 1, for i = 3 modulo 5,
the period is 2, and otherwise the period is 4. These values are all factors of
φ(5) = 4.
It is left to the reader to determine the results modulo other values, in
particular, how does Table 4 differ from the values taken modulo 7? The
period of the integer powers will be a factor of φ(7) = 6.
It is much more difficult to determine the divisibility when the values of (5)
are considered with m fixed. However, (9) shows that