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

Terms

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