1,2

Does a(n) always equal 1 + pi(n) - pi(n/2), where pi(x) is number of primes <= x? If so a(n) = A056171(n)+1. - Leroy Quet, Feb 06 2003.

This is true, because A076221(n,k) = n-1 iff either k = 1 or k is a prime with n/2 < k <= n. - Robert Israel, Aug 29 2016

Table of n, a(n) for n=1..93.

seq(1+numtheory:-pi(n) - numtheory:-pi(floor(n/2)), n=1..100); # Robert Israel, Aug 29 2016

Cf. A056171, A076221.

Sequence in context: A065067 A086411 A105528 * A215776 A140887 A132423

Adjacent sequences: A076222 A076223 A076224 * A076226 A076227 A076228

nonn

Olivier Gérard

approved