a(n) = 10 - m, where m = maximal digit of n.

Terms

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