Number of primes between n and 2n (inclusive).

Terms

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