Numbers with digits 1 and 2 and at least one of each.

Terms

a(0) =12a(1) =21a(2) =112a(3) =121a(4) =122a(5) =211a(6) =212a(7) =221a(8) =1112a(9) =1121a(10) =1122a(11) =1211a(12) =1212a(13) =1221a(14) =1222a(15) =2111a(16) =2112a(17) =2121a(18) =2122a(19) =2211a(20) =2212a(21) =2221a(22) =11112a(23) =11121a(24) =11122a(25) =11211a(26) =11212a(27) =11221a(28) =11222a(29) =12111