Loop of length 24 starting with a string of length 8
found after enumerating 27933 derivations:

.ca.aaaaaa
	rule ca -> aabc at position 0
.aabc.aaaaaa
	rule ca -> aabc at position 3
.aabaabc.aaaaa
	rule a ->  at position 3
.aababc.aaaaa
	rule a ->  at position 3
.aabbc.aaaaa
	rule ca -> aabc at position 4
.aabbaabc.aaaa
	rule bba -> ac at position 2
.aaacabc.aaaa
	rule ca -> aabc at position 6
.aaacabaabc.aaa
	rule a ->  at position 6
.aaacababc.aaa
	rule a ->  at position 6
.aaacabbc.aaa
	rule ca -> aabc at position 7
.aaacabbaabc.aa
	rule bba -> ac at position 5
.aaacaacabc.aa
	rule ca -> aabc at position 6
.aaacaaaabcbc.aa
	rule ca -> aabc at position 11
.aaacaaaabcbaabc.a
	rule a ->  at position 11
.aaacaaaabcbabc.a
	rule a ->  at position 11
.aaacaaaabcbbc.a
	rule ca -> aabc at position 12
.aaacaaaabcbbaabc.
	rule bba -> ac at position 10
.aaacaaaabcacabc.
	rule ca -> aabc at position 9
.aaacaaaabaabccabc.
	rule a ->  at position 9
.aaacaaaababccabc.
	rule a ->  at position 9
.aaacaaaabbccabc.
	rule ca -> aabc at position 11
.aaacaaaabbcaabcbc.
	rule ca -> aabc at position 10
.aaacaaaabbaabcabcbc.
	rule bba -> ac at position 8
.aaacaaaaacabcabcbc.
	rule ca -> aabc at position 9
.aaacaaaaaaabcbcabcbc.