Ternary Thue-Morse sequence: closed under a->abc, b->ac, c->b.

Terms

a(0) =3a(1) =1a(2) =2a(3) =3a(4) =2a(5) =1a(6) =3a(7) =1a(8) =2a(9) =1a(10) =3a(11) =2a(12) =3a(13) =1a(14) =2a(15) =3a(16) =2a(17) =1a(18) =3a(19) =2a(20) =3a(21) =1a(22) =2a(23) =1a(24) =3a(25) =1a(26) =2a(27) =3a(28) =2a(29) =1