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

1,1

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

Links

Table of n, a(n) for n=1..11.

Example

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

Mathematica

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

Prog

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

Crossrefs

Cf. A000040, A014076, A000720, A033271.

Sequence in context: A053313 A226404 A166825 * A365852 A042057 A214542

Adjacent sequences: A348849 A348850 A348851 * A348853 A348854 A348855

Keyword

nonn,fini,full

Author

Giorgos Kalogeropoulos, Nov 01 2021

Status

approved