A2bAb2
A3bAb3
A4bAb4
A5bAb5
2 1 1 2
3 1 1 3
4 1 1 4
5 1 1 5

 
 
A2bAb2
A3bAb3
A4bAb4
(2,2) (2,2)
(3,2) (3,2)
(3,3) (3,3)

 
 
Palindromic BFRs derived from AbAb.