Nonary
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Nonary is a base-9 numeral system, typically using the digits 0-8, but not the digit 9.
The first few numbers in nonary and decimal are:
| Nonary | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 10 | 11 | 12 | 13 | 14 |
| Decimal | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 |
The multiplication table in nonary is:
| * | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| 1 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| 2 | 2 | 4 | 6 | 8 | 11 | 13 | 15 | 17 |
| 3 | 3 | 6 | 10 | 13 | 16 | 20 | 23 | 26 |
| 4 | 4 | 8 | 13 | 17 | 22 | 26 | 31 | 35 |
| 5 | 5 | 11 | 16 | 22 | 27 | 33 | 38 | 44 |
| 6 | 6 | 13 | 20 | 26 | 33 | 40 | 46 | 53 |
| 7 | 7 | 15 | 23 | 31 | 38 | 46 | 54 | 62 |
| 8 | 8 | 17 | 26 | 35 | 44 | 53 | 62 | 71 |
Nonary notation can be used as a concise representation of ternary data. This is similar to using quaternary notation for binary data, though the digit set is closer in size to octal.
Except for three, no primes in nonary end in 0, 3 or 6, since any nonary number ending in 0, 3 or 6 is divisible by three.
A nonary number is divisible by two, four or eight, if the sum of its digits is also divisible by two, four or eight respectively.
If x is a triangular number, so is 9x+1. This means that one finds 3, 31, 311, 3111, 31111... in the triangular numbers. Likewise, 6, 61, 611, 6111, ....
The Nonary system of notation is used by the fictional civilization, The Culture, found in Iain M. Banks' books.[citation needed]
