Relative Primality

grid spacing

2

3

4

5

6

7

8

9

10

11

12

13

14

15

even

odd

all

none

Two integers are relatively prime when their only common divisor is 1. This concept can be illustrated by superimposing grids of cells with different spacings. If infinitely many grids of black cells are superimposed, so that there is a grid of spacing 2, a grid of spacing 3, and so on, then the white cells that remain are exactly those cells whose coordinates are relatively prime.