| Writing (prime(i))^j as i:j, we have the following table:
Primal Functions and Functional Digraphs for a(1) to a(15)
0756 = 1:2 2:3 4:1 || 4 -> 1 -> 2 -> 3
1176 = 1:3 2:1 4:2 || 4 -> 2 -> 1 -> 3
1188 = 1:2 2:3 5:1 || 5 -> 1 -> 2 -> 3
1200 = 1:4 2:1 3:2 || 3 -> 2 -> 1 -> 4
1400 = 1:3 3:2 4:1 || 4 -> 1 -> 3 -> 2
1404 = 1:2 2:3 6:1 || 6 -> 1 -> 2 -> 3
1620 = 1:2 2:4 3:1 || 3 -> 1 -> 2 -> 4
1836 = 1:2 2:3 7:1 || 7 -> 1 -> 2 -> 3
2052 = 1:2 2:3 8:1 || 8 -> 1 -> 2 -> 3
2160 = 1:4 2:3 3:1 || 2 -> 3 -> 1 -> 4
2200 = 1:3 3:2 5:1 || 5 -> 1 -> 3 -> 2
2400 = 1:5 2:1 3:2 || 3 -> 2 -> 1 -> 5
2484 = 1:2 2:3 9:1 || 9 -> 1 -> 2 -> 3
2600 = 1:3 3:2 6:1 || 6 -> 1 -> 3 -> 2
2904 = 1:3 2:1 5:2 || 5 -> 2 -> 1 -> 3
| 