Count from 1 to 20 (base10) using the following bases: 8, 6, 5, 3.

Base 8:

1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 20, 21, 22, 23, 24

Base 6:

1, 2, 3, 4, 5, 10, 11, 12, 13, 14, 15, 20, 21, 22, 23, 24, 25, 30, 31, 32

Base 5:

1, 2, 3, 4, 10, 11, 12, 13, 14, 20, 21, 22, 23, 24, 30, 31, 32, 33, 34, 40

Base 3:

1, 2, 10, 11, 12, 20, 21, 22, 100, 101, 102, 110, 111, 112, 120, 121, 122, 200, 201, 202

Explanation:

When counting on a certain base n you can only use n numerals (including the zero). So, if you count in base 8, you have 8 numrals, these are 0, 1, 2, 3, 4, 5, 6 and 7. The numeral 8 does not exist in base 8 the same as there is no numeral for 10 in base 10. When you're counting beyond the single numerals you add a 1 to the numeral in the column in front (which starts at zero) and reset the previous column.