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

1,2

Links

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

Formula

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

Mathematica

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

Prog

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

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.

Sequence in context: A046350 A225438 A175076 * A359596 A046315 A046372

Adjacent sequences: A046334 A046335 A046336 * A046338 A046339 A046340

Keyword

nonn

Author

Patrick De Geest, Jun 15 1998

Status

approved