A298071 Number of primes between floor(3*n/2) and 2*n (inclusive).

1, 1, 1, 1, 1, 1, 2, 1, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 3, 2, 3, 3, 3, 4, 4, 3, 4, 3, 3, 3, 4, 3, 3, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 6, 5, 5, 4, 5, 4, 5, 6, 6, 6, 7, 6, 7, 7, 7, 6, 6, 6, 6, 7, 7, 7, 7, 6, 7, 7, 7, 6, 6, 5, 6, 6, 6, 6, 7, 7, 7, 8, 8, 9, 9, 8, 9, 8, 8, 9, 10, 9

Offset: 1

Author

Bruno Berselli, Jan 11 2018

Keywords

• nonn

Crossrefs

Cf. A000040, A035250, A056171.

Programs

Mathematica

a[n_] := PrimePi[2*n] - PrimePi[Floor[3*n/2]] + If[PrimeQ[Floor[ 3*n/2]], 1, 0]; Array[a, 100] (* Jean-François Alcover, Jan 11 2018 *)

Sage

A298071 = lambda n: len([p for p in (3*n//2..2*n) if is_prime(p)])
print([A298071(n) for n in (1..97)]) # Peter Luschny, Jan 11 2018