For a given prime p, consider the positive powers of a, 0 ≤ a < p. Each value of is congruent to a number from 0 to p-1. Look for patterns.
p=11: Powers in the ring
a | ||||||||||
0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
2 | 4 | 8 | 5 | 10 | 9 | 7 | 3 | 6 | 1 | 2 |
3 | 9 | 5 | 4 | 1 | 3 | 9 | 5 | 4 | 1 | 3 |
4 | 5 | 9 | 3 | 1 | 4 | 5 | 9 | 3 | 1 | 4 |
5 | 3 | 4 | 9 | 1 | 5 | 3 | 4 | 9 | 1 | 5 |
6 | 3 | 7 | 9 | 10 | 5 | 8 | 4 | 2 | 1 | 6 |
7 | 5 | 2 | 3 | 10 | 4 | 6 | 9 | 8 | 1 | 7 |
8 | 9 | 6 | 4 | 10 | 3 | 2 | 5 | 7 | 1 | 8 |
9 | 4 | 3 | 5 | 1 | 9 | 4 | 3 | 5 | 1 | 9 |
10 | 1 | 10 | 1 | 10 | 1 | 10 | 1 | 10 | 1 | 10 |
p=17 Powers in the ring
a | ||||||||||||||||
0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
2 | 4 | 8 | 16 | 15 | 13 | 9 | 1 | 2 | 4 | 8 | 16 | 15 | 13 | 9 | 1 | 2 |
3 | 9 | 10 | 13 | 5 | 15 | 11 | 16 | 14 | 8 | 7 | 4 | 12 | 2 | 6 | 1 | 3 |
4 | 16 | 13 | 1 | 4 | 16 | 13 | 1 | 4 | 16 | 13 | 1 | 4 | 16 | 13 | 1 | 4 |
5 | 8 | 6 | 13 | 14 | 2 | 10 | 16 | 12 | 9 | 11 | 4 | 3 | 15 | 7 | 1 | 5 |
6 | 2 | 12 | 4 | 7 | 8 | 14 | 16 | 11 | 15 | 5 | 13 | 10 | 9 | 3 | 1 | 6 |
7 | 15 | 3 | 4 | 11 | 9 | 12 | 16 | 10 | 2 | 14 | 13 | 6 | 8 | 5 | 1 | 7 |
8 | 13 | 2 | 16 | 9 | 4 | 15 | 1 | 8 | 13 | 2 | 16 | 9 | 4 | 15 | 1 | 8 |
9 | 13 | 15 | 16 | 8 | 4 | 2 | 1 | 9 | 13 | 15 | 16 | 8 | 4 | 2 | 1 | 9 |
10 | 15 | 14 | 4 | 6 | 9 | 5 | 16 | 7 | 2 | 3 | 13 | 11 | 8 | 12 | 1 | 10 |
11 | 2 | 5 | 4 | 10 | 8 | 3 | 16 | 6 | 15 | 12 | 13 | 7 | 9 | 14 | 1 | 11 |
12 | 8 | 11 | 13 | 3 | 2 | 7 | 16 | 5 | 9 | 6 | 4 | 14 | 15 | 10 | 1 | 12 |
13 | 16 | 4 | 1 | 13 | 16 | 4 | 1 | 13 | 16 | 4 | 1 | 13 | 16 | 4 | 1 | 13 |
14 | 9 | 7 | 13 | 12 | 15 | 6 | 16 | 3 | 8 | 10 | 4 | 5 | 2 | 11 | 1 | 14 |
15 | 4 | 9 | 16 | 2 | 13 | 8 | 1 | 15 | 4 | 9 | 16 | 2 | 13 | 8 | 1 | 15 |
16 | 1 | 16 | 1 | 16 | 1 | 16 | 1 | 16 | 1 | 16 | 1 | 16 | 1 | 16 | 1 | 16 |
One of the patterns that you might have noticed is indeed a theorem