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A110893 Numbers with a semiprime number of prime divisors (counted with multiplicity). 3
16, 24, 36, 40, 54, 56, 60, 64, 81, 84, 88, 90, 96, 100, 104, 126, 132, 135, 136, 140, 144, 150, 152, 156, 160, 184, 189, 196, 198, 204, 210, 216, 220, 224, 225, 228, 232, 234, 240, 248, 250, 260, 276, 294, 296, 297, 306, 308, 315, 324, 328, 330, 336, 340, 342 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

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

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

FORMULA

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, ...]

PROG

(PARI) is(n)=n>9 && bigomega(bigomega(n))==2 \\ Charles R Greathouse IV, Jan 31 2017

CROSSREFS

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

Sequence in context: A206260 A036328 A067028 * A014613 A046370 A103248

Adjacent sequences:  A110890 A110891 A110892 * A110894 A110895 A110896

KEYWORD

easy,nonn

AUTHOR

Jonathan Vos Post, Sep 20 2005

STATUS

approved

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Last modified August 14 21:07 EDT 2018. Contains 313756 sequences. (Running on oeis4.)