A237990 - OEIS

A237990

Numbers m such that the numbers of primes, even positive integers and odd positive integers less than or equal to m are all even.

%I #19 Jun 24 2024 08:47:42

%S 4,8,16,20,40,44,56,64,72,80,92,96,108,116,120,124,132,136,140,144,

%T 148,152,156,164,176,184,188,196,200,204,208,224,232,240,252,256,264,

%U 268,272

%N Numbers m such that the numbers of primes, even positive integers and odd positive integers less than or equal to m are all even.

%C A subsequence of A008586.

%H Ivan N. Ianakiev, <a href="/A237990/b237990.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) == 0 (mod 4)

%e A tetrahedral die whose faces are marked with the numbers from 1 to 4 has an even number of sides marked with prime numbers, even integers and odd integers. Therefore, 4 is in the sequence.

%t Select[Range[4, 1000, 4], EvenQ[PrimePi[#]] &] (* _Paolo Xausa_, Jun 24 2024 *)

%Y Cf. A008586, A237989.

%K nonn,easy

%O 1,1

%A _Ivan N. Ianakiev_, Feb 16 2014