rule:

Some neat ones:

0 1 0 0 4 1 4 4 0 0 1 1 2
0 4 0 3 0 1 1 1 0 2 3 1 2
3 2 3 0 0 3 2 2 3 1 4 2 4
0 2 3 2 1 2 2 3 0 2 1 0 2
4 3 0 1 4 1 3 1 1 2 4 3 1 (keep generating until you get oscillation)