A110893 - OEIS

%I #5 Jan 31 2017 14:27:07

%S 16,24,36,40,54,56,60,64,81,84,88,90,96,100,104,126,132,135,136,140,

%T 144,150,152,156,160,184,189,196,198,204,210,216,220,224,225,228,232,

%U 234,240,248,250,260,276,294,296,297,306,308,315,324,328,330,336,340,342

%N Numbers with a semiprime number of prime divisors (counted with multiplicity).

%C Below 256 = 2^8 this is identical to A067028 (Numbers with a composite number of prime factors, counted with multiplicity).

%H Charles R Greathouse IV, <a href="/A110893/b110893.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) such that A001222(a(n)) is an element of A001358. a(n) such that bigomega(a(n)) is an element of A001358. Union[4-almost primes(A014613), 6-almost primes(A046306), 9-almost primes(A046312), 10-almost primes(A046314), 14-almost primes(A069275), 15-almost primes(A069276), 21-almost primes, 22-almost primes, 25-almost primes, 26-almost primes, ...]

%o (PARI) is(n)=n>9 && bigomega(bigomega(n))==2 \\ _Charles R Greathouse IV_, Jan 31 2017

%Y Cf. A000040, A001222, A001358, A014613, A046306, A046312, A046314, A063989, A067028, A069276.

%K easy,nonn

%O 1,1

%A _Jonathan Vos Post_, Sep 20 2005