Katadromes: digits in base 7 are in strict descending order.

Terms

a(0) =0a(1) =1a(2) =2a(3) =3a(4) =4a(5) =5a(6) =6a(7) =7a(8) =14a(9) =15a(10) =21a(11) =22a(12) =23a(13) =28a(14) =29a(15) =30a(16) =31a(17) =35a(18) =36a(19) =37a(20) =38a(21) =39a(22) =42a(23) =43a(24) =44a(25) =45a(26) =46a(27) =47a(28) =105a(29) =154