Loop of length 7 starting with a string of length 13
found after enumerating 155 derivations:

.bbbb.bbbbbbbbb
	rule bbbb -> aabab at position 0
.aabab.bbbbbbbbb
	rule bbbb -> aabab at position 4
.aabaaabab.bbbbbb
	rule aaa -> bbb at position 3
.aabbbbbab.bbbbbb
	rule bbbb -> aabab at position 8
.aabbbbbaaabab.bbb
	rule aaa -> bbb at position 7
.aabbbbbbbbbab.bbb
	rule bbbb -> aabab at position 12
.aabbbbbbbbbaaabab.
	rule aaa -> bbb at position 11
.aabbbbbbbbbbbbbab.