A374044 - OEIS

%I #15 Jun 28 2024 04:53:12

%S 1,5,7,8,11,13,17,19,23,25,29,31,35,37,40,41,43,47,49,53,55,56,59,61,

%T 64,65,67,71,73,77,79,83,85,88,89,91,95,97,101,103,104,107,109,113,

%U 115,119,121,125,127,131,133,136,137,139,143,145,149,151,152,155,157,161,163,167,169,173,175,179,181,184,185,187

%N Non-multiples of 3 whose 2-adic valuation is a multiple of 3.

%C A multiplicative semigroup: if m and n are in the sequence, then so is m*n.

%C The asymptotic density of this sequence is 8/21. - _Amiram Eldar_, Jun 28 2024

%H Antti Karttunen, <a href="/A374044/b374044.txt">Table of n, a(n) for n = 1..12000</a>

%F {k | A007814(k) == 0 (mod 3), A007949(k) = 0}.

%t Select[Range[200], !Divisible[#, 3] && Divisible[IntegerExponent[#, 2], 3] &] (* _Amiram Eldar_, Jun 28 2024 *)

%o (PARI) isA374044 = A374043;

%Y Cf. A007814, A007949, A374043 (characteristic function).

%Y Intersection of A001651 and A191257.

%Y Subsequence of A339746, of A373992, and of A374042.

%K nonn,easy

%O 1,2

%A _Antti Karttunen_, Jun 27 2024