A374042 - OEIS

%I #11 Jun 27 2024 18:13:11

%S 1,5,7,8,11,13,17,19,23,25,27,29,31,35,36,37,40,41,43,47,49,53,55,56,

%T 59,61,64,65,67,71,73,77,79,83,85,88,89,91,95,97,101,103,104,107,109,

%U 113,115,119,121,125,127,131,133,135,136,137,139,143,145,149,151,152,155,157,161,162,163,167,169,173,175,179

%N Numbers k such that A276085(k) and A328768(k) are both multiples of 3, where A276085 is the primorial base log-function, and A328768 is the first primorial based variant of arithmetic derivative.

%C Numbers whose 3-adic valuation is not 1 and whose 2-adic and 3-adic valuations are equal modulo 3.

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

%H Antti Karttunen, <a href="/A374042/b374042.txt">Table of n, a(n) for n = 1..12000</a>

%H <a href="/index/Pri#primorial_numbers">Index entries for sequences related to primorial numbers</a>

%F {k | A007814(k) == A007949(n) (mod 3), A007949(k) != 1}.

%o (PARI) isA374042 = A374041;

%Y Intersection of A339746 and A373992.

%Y Positions of multiples of 3 in A374031.

%Y Cf. A276085, A328768, A374041 (characteristic function), A374044 (subsequence).

%K nonn

%O 1,2

%A _Antti Karttunen_, Jun 26 2024