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

1,2

Links

Table of n, a(n) for n=1..70.

Index entries for sequences where odd perfect numbers must occur, if they exist at all

Index entries for sequences related to sigma(n)

Prog

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

Crossrefs

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

Cf. A000203, A001222, A358768 (complement).

Cf. also A359167, A359168.

Sequence in context: A276527 A020643 A131354 * A092360 A129141 A289013

Adjacent sequences: A358764 A358765 A358766 * A358768 A358769 A358770

Keyword

nonn

Author

Antti Karttunen, Dec 19 2022

Status

approved