Number of odd primes <= n.

Terms

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