Ternary numbers consisting of a run of 1's, then a run of 2's, then a run of 0's.

Terms

a(0) =120a(1) =1120a(2) =1200a(3) =1220a(4) =11120a(5) =11200a(6) =11220a(7) =12000a(8) =12200a(9) =12220a(10) =111120a(11) =111200a(12) =111220a(13) =112000a(14) =112200a(15) =112220a(16) =120000a(17) =122000a(18) =122200a(19) =122220a(20) =1111120a(21) =1111200a(22) =1111220a(23) =1112000a(24) =1112200a(25) =1112220a(26) =1120000a(27) =1122000a(28) =1122200a(29) =1122220