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A214195
Numbers with the number of distinct prime factors a multiple of 3.
2
1, 30, 42, 60, 66, 70, 78, 84, 90, 102, 105, 110, 114, 120, 126, 130, 132, 138, 140, 150, 154, 156, 165, 168, 170, 174, 180, 182, 186, 190, 195, 198, 204, 220, 222, 228, 230, 231, 234, 238, 240, 246, 252, 255, 258, 260, 264, 266, 270, 273, 276, 280, 282, 285
OFFSET
1,2
COMMENTS
If GCD(a(n),a(m))=1, then a(n)*a(m) is also in this sequence. - Enrique Pérez Herrero, Nov 23 2013
LINKS
Enrique Pérez Herrero, Table of n, a(n) for n = 1..5000
FORMULA
A010872(A001221(a(n))) = 0.
MATHEMATICA
Select[Range[1000], Mod[PrimeNu[#], 3]==0&]
PROG
(PARI) is(n)=omega(n)%3==0 \\ Charles R Greathouse IV, Sep 14 2015
CROSSREFS
Subsequences include A033992, A067885, A007304 and A147573.
Sequence in context: A114816 A299991 A000977 * A033992 A360525 A308127
KEYWORD
nonn
AUTHOR
STATUS
approved