A328003 a(n) = ppi(2*n) - ppi(n). Number of prime powers (A246655) in the interval (n, 2*n]. See comments.

0, 1, 2, 2, 3, 3, 4, 4, 4, 4, 5, 4, 5, 5, 6, 7, 8, 7, 7, 7, 7, 8, 9, 8, 9, 9, 9, 9, 9, 8, 9, 9, 9, 9, 10, 10, 11, 11, 11, 11, 12, 12, 13, 12, 12, 13, 13, 12, 12, 12, 12, 13, 14, 13, 14, 15, 15, 16, 16, 15, 15, 15, 15, 16, 17, 17, 18, 17, 17, 18, 19, 18, 18

Offset

0,3

Comments

The sequence counts prime powers greater than n up to and including 2*n. - Harvey P. Dale, Aug 01 2020

Links

Table of n, a(n) for n=0..72.

Mathematica

Table[Count[Range[n+1, 2n], _?PrimePowerQ], {n, 0, 80}] (* Harvey P. Dale, Aug 01 2020 *)

Prog

(SageMath)
def a(n) : return sum([1 for k in (n+1..2*n) if is_prime_power(k)])
print([a(n) for n in (0..72)])

Crossrefs

Cf. A108954, A025528, A246655.

Sequence in context: A171896 A341167 A094235 * A262558 A156876 A137397

Adjacent sequences: A328000 A328001 A328002 * A328004 A328005 A328006

Keyword

nonn

Author

Peter Luschny, Nov 18 2019

Status

approved