cp's OEIS Frontend

A359168 Numbers k for which there is an odd number of prime factors (when counted with multiplicity) in k*sigma(k), where sigma is the sum of divisors function.

%I A359168 #5 Dec 19 2022 15:07:50
%S A359168 3,4,5,6,8,9,10,13,16,18,21,23,25,26,27,28,33,35,37,42,44,46,50,51,53,
%T A359168 54,55,56,57,59,60,61,63,64,66,68,70,73,74,76,83,85,87,88,89,91,93,95,
%U A359168 96,99,102,103,106,110,112,114,116,118,120,122,123,124,125,126,129,131,136,139,141,143,145,146
%N A359168 Numbers k for which there is an odd number of prime factors (when counted with multiplicity) in k*sigma(k), where sigma is the sum of divisors function.
%C A359168 Numbers k such that the parities of A001222(k) and A058063(k) differ.
%H A359168 <a href="/index/O#opnseqs">Index entries for sequences where odd perfect numbers must occur, if they exist at all</a>
%H A359168 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%o A359168 (PARI) isA359168(n) = ((bigomega(n)+bigomega(sigma(n)))%2);
%Y A359168 Positions of -1's in A359166.
%Y A359168 Cf. A000203, A001222, A058063, A359167 (complement).
%Y A359168 Cf. also A358767, A358768.
%Y A359168 Cf. A000396, A005820, A046060, A065997 (subsequences).
%K A359168 nonn
%O A359168 1,1
%A A359168 _Antti Karttunen_, Dec 19 2022