A214195 - OEIS

%I #18 Sep 14 2015 09:23:45

%S 1,30,42,60,66,70,78,84,90,102,105,110,114,120,126,130,132,138,140,

%T 150,154,156,165,168,170,174,180,182,186,190,195,198,204,220,222,228,

%U 230,231,234,238,240,246,252,255,258,260,264,266,270,273,276,280,282,285

%N Numbers with the number of distinct prime factors a multiple of 3.

%C If GCD(a(n),a(m))=1, then a(n)*a(m) is also in this sequence. -  _Enrique Pérez Herrero_, Nov 23 2013

%H Enrique Pérez Herrero, <a href="/A214195/b214195.txt">Table of n, a(n) for n = 1..5000</a>

%F A010872(A001221(a(n))) = 0.

%t Select[Range[1000],Mod[PrimeNu[#],3]==0&]

%o (PARI) is(n)=omega(n)%3==0 \\ _Charles R Greathouse IV_, Sep 14 2015

%Y Subsequences include A033992, A067885, A007304 and A147573.

%Y Cf. A145784, A030230, A030231.

%K nonn

%O 1,2

%A _Enrique Pérez Herrero_, Jul 07 2012