A348852 Numbers k such that the number of odd nonprimes <= k is equal to the number of primes <= k.

2, 93, 94, 97, 98, 101, 102, 105, 106, 117, 118

Offset: 1

Author

Giorgos Kalogeropoulos, Nov 01 2021

Keywords

• nonn
• fini
• full

Comments

This sequence is finite. For k > 118, there are always more odd nonprimes than primes <= k.

Numbers k such that A000720(k) = A033271(k). - Michel Marcus, Nov 06 2021

Examples

			a(4) = 97 is a term because there are 25 odd nonprimes <= 97 and 25 primes <= 97.
		

Crossrefs

Cf. A000040, A014076, A000720, A033271.

Programs

Mathematica

Select[Range@1000,(k=#;Length@Select[Range@k,OddQ@#&&!PrimeQ@#&]==PrimePi@k)&]

PARI

isok(k) = primepi(k) == #select(x->(!isprime(x) && (x%2)), [1..k]); \\ Michel Marcus, Nov 06 2021