Number of prime powers <= n with exponents > 0 (A246655).

Terms

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