Nonnegative integers in balanced ternary representation (with 2 standing for -1 digit).

Terms

a(0) =0a(1) =1a(2) =12a(3) =10a(4) =11a(5) =122a(6) =120a(7) =121a(8) =102a(9) =100a(10) =101a(11) =112a(12) =110a(13) =111a(14) =1222a(15) =1220a(16) =1221a(17) =1202a(18) =1200a(19) =1201a(20) =1212a(21) =1210a(22) =1211a(23) =1022a(24) =1020a(25) =1021a(26) =1002a(27) =1000a(28) =1001a(29) =1012