Numbers with digits in strictly decreasing order, sorted lexicographically.

Terms

a(0) =0a(1) =1a(2) =10a(3) =2a(4) =20a(5) =21a(6) =210a(7) =3a(8) =30a(9) =31a(10) =310a(11) =32a(12) =320a(13) =321a(14) =3210a(15) =4a(16) =40a(17) =41a(18) =410a(19) =42a(20) =420a(21) =421a(22) =4210a(23) =43a(24) =430a(25) =431a(26) =4310a(27) =432a(28) =4320a(29) =4321