Katadromes: digits in base 13 are in strict descending order.

Terms

a(0) =0a(1) =1a(2) =2a(3) =3a(4) =4a(5) =5a(6) =6a(7) =7a(8) =8a(9) =9a(10) =10a(11) =11a(12) =12a(13) =13a(14) =26a(15) =27a(16) =39a(17) =40a(18) =41a(19) =52a(20) =53a(21) =54a(22) =55a(23) =65a(24) =66a(25) =67a(26) =68a(27) =69a(28) =78a(29) =79