A358768 - OEIS

%I #4 Dec 19 2022 15:07:13

%S 2,4,6,7,9,10,11,12,16,17,19,20,21,25,26,29,30,31,32,33,35,41,43,45,

%T 46,47,48,51,52,54,55,56,57,60,64,67,71,72,74,75,78,79,80,85,87,88,91,

%U 92,93,95,96,97,98,101,105,106,107,108,109,113,117,118,122,123,126,127,128,129,130,136,137,138

%N Numbers k with an odd number of prime factors (when counted with multiplicity) in sigma(k), the sum of divisors of k.

%H <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>

%o (PARI) isA358768(n) = (bigomega(sigma(n))%2);

%Y Positions of odd terms in A058063. Positions of -1's in A358766.

%Y Cf. A000203, A001222, A358767 (complement).

%K nonn

%O 1,1

%A _Antti Karttunen_, Dec 19 2022