Numbers with digits in nonincreasing 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) =20a(13) =21a(14) =22a(15) =30a(16) =31a(17) =32a(18) =33a(19) =40a(20) =41a(21) =42a(22) =43a(23) =44a(24) =50a(25) =51a(26) =52a(27) =53a(28) =54a(29) =55