A358767 Numbers k with an even number of prime factors (when counted with multiplicity) in sigma(k), the sum of divisors of k.

1, 3, 5, 8, 13, 14, 15, 18, 22, 23, 24, 27, 28, 34, 36, 37, 38, 39, 40, 42, 44, 49, 50, 53, 58, 59, 61, 62, 63, 65, 66, 68, 69, 70, 73, 76, 77, 81, 82, 83, 84, 86, 89, 90, 94, 99, 100, 102, 103, 104, 110, 111, 112, 114, 115, 116, 119, 120, 121, 124, 125, 131, 132, 133, 134, 135, 139, 140, 142, 144

Offset: 1

Author

Antti Karttunen, Dec 19 2022

Keywords

• nonn

Links

• Index entries for sequences where odd perfect numbers must occur, if they exist at all
• Index entries for sequences related to sigma(n)

Crossrefs

Positions of even terms in A058063. Positions of 1's in A358766.

Cf. A000203, A001222, A358768 (complement).

Cf. also A359167, A359168.

Programs

PARI

isA358767(n) = !(bigomega(sigma(n))%2);