Length of Roman notation for n < length of decimal representation.

Terms

a(0) =10a(1) =50a(2) =100a(3) =101a(4) =105a(5) =110a(6) =150a(7) =200a(8) =400a(9) =500a(10) =501a(11) =505a(12) =510a(13) =550a(14) =600a(15) =900a(16) =1000a(17) =1001a(18) =1002a(19) =1004a(20) =1005a(21) =1006a(22) =1009a(23) =1010a(24) =1011a(25) =1015a(26) =1020a(27) =1040a(28) =1050a(29) =1051