cp's OEIS Frontend

A373259 Numbers k such that k' / gcd(k,k') is a multiple of 4 and A276085(k) is a multiple of 8, where k' stands for the arithmetic derivative of k, A003415, and A276085 is the primorial base log-function.

%I A373259 #8 Jun 02 2024 10:16:57
%S A373259 1,15,28,39,51,55,76,81,87,115,124,143,144,183,187,188,215,219,225,
%T A373259 256,259,267,268,287,291,295,297,299,303,316,319,327,339,355,371,391,
%U A373259 400,411,412,415,420,441,471,508,519,528,535,556,559,579,585,591,621,625,652,655,667,671,687,699,703,716,731,755,765,767
%N A373259 Numbers k such that k' / gcd(k,k') is a multiple of 4 and A276085(k) is a multiple of 8, where k' stands for the arithmetic derivative of k, A003415, and A276085 is the primorial base log-function.
%C A373259 This is a multiplicative semigroup; if m and n are in the sequence then so is m*n.
%H A373259 Antti Karttunen, <a href="/A373259/b373259.txt">Table of n, a(n) for n = 1..10000</a>
%o A373259 (PARI) isA373259 = A373258;
%Y A373259 Intersection of A369005 and A373138.
%Y A373259 Subsequence of A369002.
%Y A373259 Cf. A002110, A003415, A083345, A276085, A373258 (characteristic function).
%K A373259 nonn
%O A373259 1,2
%A A373259 _Antti Karttunen_, Jun 02 2024