A282029 a(n) = n - pi(n/2).

0, 1, 2, 3, 3, 4, 4, 5, 6, 7, 7, 8, 9, 10, 10, 11, 12, 13, 14, 15, 16, 17, 17, 18, 19, 20, 20, 21, 22, 23, 24, 25, 26, 27, 27, 28, 29, 30, 30, 31, 32, 33, 34, 35, 36, 37, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 48, 49, 50, 51, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 62, 63, 64, 65, 66, 67, 68

Offset: 0

Author

N. J. A. Sloane, Feb 17 2017

Keywords

• nonn

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A000720, A282028.

Programs

Magma

[0,1] cat [ n-#PrimesUpTo(n div 2): n in [2..90] ]; // Vincenzo Librandi, Feb 18 2017

Mathematica

Table[n - PrimePi[n/2], {n, 0, 100}] (* Vincenzo Librandi, Feb 18 2017 *)

PARI

a(n)=n - primepi(n\2) \\ Charles R Greathouse IV, Feb 18 2017