Count upwards in binary.

Example:

0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
etc...

So, I'll start with 0000 0000 0000

Next will be 0000 0000 0001

(Let's try and get to 1111 1111 1111!)