Metadromes: digits in base 16 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) =9a(10) =10a(11) =11a(12) =12a(13) =13a(14) =14a(15) =15a(16) =18a(17) =19a(18) =20a(19) =21a(20) =22a(21) =23a(22) =24a(23) =25a(24) =26a(25) =27a(26) =28a(27) =29a(28) =30a(29) =31