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Odd number

An odd number cannot be divided by two.

 


Explanation

The Greeks called odd numbers gnomons. A gnomon is a hook on a sundial.

11
9
7
5
3
1

In the hooks are an odd number of bullets. Every odd number is the difference of two squares, because 2n + 1 = (n + 1)2 − n2 and that gives

1 = 12 - 02
3 = 22 - 12
5 = 32 - 22
7 = 42 - 32
9 = 52 - 42
11 = 62 - 52

 


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