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

Terms

a(0) =1a(1) =5a(2) =10a(3) =11a(4) =15a(5) =20a(6) =40a(7) =50a(8) =51a(9) =55a(10) =60a(11) =90a(12) =100a(13) =101a(14) =102a(15) =104a(16) =105a(17) =106a(18) =109a(19) =110a(20) =111a(21) =115a(22) =120a(23) =140a(24) =150a(25) =151a(26) =155a(27) =160a(28) =190a(29) =200