%I
%S 210,330,390,420,462,510,546,570,630,660,690,714,770,780,798,840,858,
%T 870,910,924,930,966,990,1020,1050,1092,1110,1122,1140,1155,1170,1190,
%U 1218,1230,1254,1260,1290,1302,1320,1326,1330,1365,1380,1386,1410,1428
%N Numbers that are divisible by exactly four different primes.
%C For a(n) < 30030 = 2 * 3 * 5 * 7 * 11 * 13 this is identical to "numbers with a semiprime number of distinct prime factors."  _Jonathan Vos Post_, Sep 21 2005
%H T. D. Noe, <a href="/A033993/b033993.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) has exactly 4 distinct prime factors. omega(a(n)) = A001221(a(n)) = 4.  _Jonathan Vos Post_, Sep 21 2005
%e The 4th primorial is the first term of this sequence: A002110(4) = 210.
%t Select[Range[1500], Length[FactorInteger[#]] == 4 &] (* _Vladimir Joseph Stephan Orlovsky_, Apr 22 2010 *)
%o (PARI) is(n)=omega(n)==4 \\ _Charles R Greathouse IV_, Sep 17 2015
%Y Cf. A000977, A007774, A000961, A002110, A033992, A051270, A001221.
%K nonn,easy
%O 1,1
%A _Labos Elemer_
