a(n) = t(2+3n), where t = A001285 (Thue-Morse sequence).

Terms

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