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

Terms

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