Numbers with exactly two distinct base-9 digits.

Terms

a(0) =9a(1) =11a(2) =12a(3) =13a(4) =14a(5) =15a(6) =16a(7) =17a(8) =18a(9) =19a(10) =21a(11) =22a(12) =23a(13) =24a(14) =25a(15) =26a(16) =27a(17) =28a(18) =29a(19) =31a(20) =32a(21) =33a(22) =34a(23) =35a(24) =36a(25) =37a(26) =38a(27) =39a(28) =41a(29) =42