cp's OEIS Frontend

A359167 Numbers k for which there is an even number of prime factors (when counted with multiplicity) in k*sigma(k), where sigma is the sum of divisors function.

%I A359167 #7 Dec 19 2022 15:07:45
%S A359167 1,2,7,11,12,14,15,17,19,20,22,24,29,30,31,32,34,36,38,39,40,41,43,45,
%T A359167 47,48,49,52,58,62,65,67,69,71,72,75,77,78,79,80,81,82,84,86,90,92,94,
%U A359167 97,98,100,101,104,105,107,108,109,111,113,115,117,119,121,127,128,130,132,133,134,135,137,138
%N A359167 Numbers k for which there is an even number of prime factors (when counted with multiplicity) in k*sigma(k), where sigma is the sum of divisors function.
%C A359167 Numbers k such that the parities of A001222(k) and A058063(k) are equal.
%H A359167 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%o A359167 (PARI) isA359167(n) = !((bigomega(n)+bigomega(sigma(n)))%2);
%Y A359167 Positions of 1's in A359166.
%Y A359167 Cf. A000203, A001222, A058063, A359168 (complement).
%K A359167 nonn
%O A359167 1,2
%A A359167 _Antti Karttunen_, Dec 19 2022