Metadromes: digits in base 9 are in strict ascending order.

Terms

a(0) =0a(1) =1a(2) =2a(3) =3a(4) =4a(5) =5a(6) =6a(7) =7a(8) =8a(9) =11a(10) =12a(11) =13a(12) =14a(13) =15a(14) =16a(15) =17a(16) =21a(17) =22a(18) =23a(19) =24a(20) =25a(21) =26a(22) =31a(23) =32a(24) =33a(25) =34a(26) =35a(27) =41a(28) =42a(29) =43