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

1,1

Links

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

Example

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

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 *)

Crossrefs

Cf. A001221, A098902, A098903, A098905.

Sequence in context: A292793 A332835 A018469 * A248846 A046127 A271480

Adjacent sequences: A098901 A098902 A098903 * A098905 A098906 A098907

Keyword

easy,nonn

Author

Shyam Sunder Gupta, Oct 14 2004

Status

approved