A098904 Even numbers whose number of distinct prime factors is odd.

2, 4, 8, 16, 30, 32, 42, 60, 64, 66, 70, 78, 84, 90, 102, 110, 114, 120, 126, 128, 130, 132, 138, 140, 150, 154, 156, 168, 170, 174, 180, 182, 186, 190, 198, 204, 220, 222, 228, 230, 234, 238, 240, 246, 252, 256, 258, 260, 264, 266, 270, 276, 280, 282, 286, 290

Offset: 1

Author

Shyam Sunder Gupta, Oct 14 2004

Keywords

• easy
• nonn

Examples

			30 is a member of sequence because 30 is even and number of distinct prime factors of 30, i.e., 3 is odd.
		

Links

• G. C. Greubel, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A001221, A098902, A098903, A098905.

Programs

Mathematica

Select[Select[Range[500], OddQ[PrimeNu[#]] &], EvenQ] (* G. C. Greubel, May 21 2017 *)
Select[2*Range[150],OddQ[PrimeNu[#]]&] (* Harvey P. Dale, Aug 15 2020 *)

PARI

is(k) = !(k % 2) && omega(k) % 2; \\ Amiram Eldar, Sep 18 2024