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

1,2

Comments

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

Links

Table of n, a(n) for n=1..71.

Index entries for sequences related to sigma(n)

Prog

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

Crossrefs

Positions of 1's in A359166.

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

Sequence in context: A226089 A208846 A087723 * A299242 A184792 A136998

Adjacent sequences: A359164 A359165 A359166 * A359168 A359169 A359170

Keyword

nonn

Author

Antti Karttunen, Dec 19 2022

Status

approved