a(n) = ceiling(1000*log_10(n)).

Terms

a(0) =0a(1) =302a(2) =478a(3) =603a(4) =699a(5) =779a(6) =846a(7) =904a(8) =955a(9) =1000a(10) =1042a(11) =1080a(12) =1114a(13) =1147a(14) =1177a(15) =1205a(16) =1231a(17) =1256a(18) =1279a(19) =1302a(20) =1323a(21) =1343a(22) =1362a(23) =1381a(24) =1398a(25) =1415a(26) =1432a(27) =1448a(28) =1463a(29) =1478