Counting from 0-15 in binary

0 - 0
1 - 1
2 - 10
3 - 11
4 - 100
5 - 101
6 - 110
7 - 111
8 - 1000
9 - 1001
10 - 1010
11 - 1011
12 - 1100
13 - 1101
14 - 1110
15 - 1111