In base 12 those are just the columns for 1, 5, 7, and 11, the only numbers between 1 and 12 that aren't divisible by any of 12s factors. If you do this for any

In base 12 those are just the columns for 1, 5, 7, and 11, the only numbers between 1 and 12 that aren't divisible by any of 12s factors. If you do this for any base the prime numbers will fall in columns like those. Note that there aren't any prime numbers ending in 2 or 5 in base 10 (except 2 and 5), in base 12 it would be the same for numbers ending in 2, 3, 4, 6, 8, 9 and 10.