Numbers with exactly two distinct base-7 digits.

Terms

a(0) =7a(1) =9a(2) =10a(3) =11a(4) =12a(5) =13a(6) =14a(7) =15a(8) =17a(9) =18a(10) =19a(11) =20a(12) =21a(13) =22a(14) =23a(15) =25a(16) =26a(17) =27a(18) =28a(19) =29a(20) =30a(21) =31a(22) =33a(23) =34a(24) =35a(25) =36a(26) =37a(27) =38a(28) =39a(29) =41