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

Terms

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