A358768 Numbers k with an odd number of prime factors (when counted with multiplicity) in sigma(k), the sum of divisors of k.

2, 4, 6, 7, 9, 10, 11, 12, 16, 17, 19, 20, 21, 25, 26, 29, 30, 31, 32, 33, 35, 41, 43, 45, 46, 47, 48, 51, 52, 54, 55, 56, 57, 60, 64, 67, 71, 72, 74, 75, 78, 79, 80, 85, 87, 88, 91, 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

Offset

1,1

Links

Table of n, a(n) for n=1..72.

Index entries for sequences related to sigma(n)

Prog

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

Crossrefs

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

Cf. A000203, A001222, A358767 (complement).

Sequence in context: A048284 A026516 A289012 * A186493 A289072 A287379

Adjacent sequences: A358765 A358766 A358767 * A358769 A358770 A358771

Keyword

nonn

Author

Antti Karttunen, Dec 19 2022

Status

approved