A046337 Odd numbers with an even number of prime factors (counted with multiplicity).

1, 9, 15, 21, 25, 33, 35, 39, 49, 51, 55, 57, 65, 69, 77, 81, 85, 87, 91, 93, 95, 111, 115, 119, 121, 123, 129, 133, 135, 141, 143, 145, 155, 159, 161, 169, 177, 183, 185, 187, 189, 201, 203, 205, 209, 213, 215, 217, 219, 221, 225, 235, 237, 247, 249, 253, 259

Offset: 1

Author

Patrick De Geest, Jun 15 1998

Keywords

• nonn

Links

• John Cerkan, Table of n, a(n) for n = 1..10000

Crossrefs

Intersection of A005408 and A028260.

Setwise difference A005408 \ A067019.

Setwise difference A028260 \ A063745.

Union of A359161 and A359163.

Union of A327862 and A360110.

Subsequence of A345452, of A356312 and of A359371.

Positions of positive terms in A166698, positions of even terms in A327858 and A356299.

Subsequences: A002557, A046315 (odd semiprimes), A056913, A359596, A359607, A359608 (without its term 2).

Cf. A000035, A008836, A046338, A046470, A353557 (characteristic function), A358777.

Cf. also A036349, A297845.

Programs

Mathematica

Select[Range[1,301,2],EvenQ[PrimeOmega[#]]&] (* Harvey P. Dale, Jul 25 2011 *)

PARI

lista(nn) = {forstep(n=1, nn, 2, if (bigomega(n) % 2 == 0, print1(n, ", ")));} \\ Michel Marcus, Jul 04 2015

Formula

{k | A000035(k) > 0 and A008836(k) > 0}. - Antti Karttunen, Jan 13 2023