OFFSET
1,1
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..1000
EXAMPLE
21 is a member of sequence because 21 is odd and number of distinct prime factors of 21, i.e., 2 is even.
MATHEMATICA
Select[Select[Range[2, 400], EvenQ[PrimeNu[#]] &], OddQ] (* G. C. Greubel, May 09 2017 *)
Select[Range[3, 250, 2], EvenQ[PrimeNu[#]]&] (* Harvey P. Dale, Jan 19 2020 *)
PROG
(PARI) isok(n) = (n>1) && (n%2) && !(omega(n) % 2); \\ Michel Marcus, Jan 20 2020
(Magma) [k:k in [3..250 by 2]|IsEven(#PrimeDivisors(k))]; // Marius A. Burtea, Jan 20 2020
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Shyam Sunder Gupta, Oct 14 2004
STATUS
approved