Numbers with digits in strictly decreasing order. From the Macaulay expansion of n.

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) =20a(12) =21a(13) =30a(14) =31a(15) =32a(16) =40a(17) =41a(18) =42a(19) =43a(20) =50a(21) =51a(22) =52a(23) =53a(24) =54a(25) =60a(26) =61a(27) =62a(28) =63a(29) =64