a(n) = floor(10*log_2(n)).

Terms

a(0) =0a(1) =10a(2) =15a(3) =20a(4) =23a(5) =25a(6) =28a(7) =30a(8) =31a(9) =33a(10) =34a(11) =35a(12) =37a(13) =38a(14) =39a(15) =40a(16) =40a(17) =41a(18) =42a(19) =43a(20) =43a(21) =44a(22) =45a(23) =45a(24) =46a(25) =47a(26) =47a(27) =48a(28) =48a(29) =49