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.

1, 2, 7, 11, 12, 14, 15, 17, 19, 20, 22, 24, 29, 30, 31, 32, 34, 36, 38, 39, 40, 41, 43, 45, 47, 48, 49, 52, 58, 62, 65, 67, 69, 71, 72, 75, 77, 78, 79, 80, 81, 82, 84, 86, 90, 92, 94, 97, 98, 100, 101, 104, 105, 107, 108, 109, 111, 113, 115, 117, 119, 121, 127, 128, 130, 132, 133, 134, 135, 137, 138

Offset: 1

Author

Antti Karttunen, Dec 19 2022

Keywords

• nonn

Comments

Numbers k such that the parities of A001222(k) and A058063(k) are equal.

Links

• Index entries for sequences related to sigma(n)

Crossrefs

Positions of 1's in A359166.

Cf. A000203, A001222, A058063, A359168 (complement).

Programs

PARI

isA359167(n) = !((bigomega(n)+bigomega(sigma(n)))%2);