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A046339 Composite numbers with an odd number of prime factors (counted with multiplicity). 5
8, 12, 18, 20, 27, 28, 30, 32, 42, 44, 45, 48, 50, 52, 63, 66, 68, 70, 72, 75, 76, 78, 80, 92, 98, 99, 102, 105, 108, 110, 112, 114, 116, 117, 120, 124, 125, 128, 130, 138, 147, 148, 153, 154, 162, 164, 165, 168, 170, 171, 172, 174, 175, 176, 180, 182, 186, 188 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

John Cerkan, Table of n, a(n) for n = 1..10000

EXAMPLE

a(1)=8 as 8=2*2*2, that is 8 is a composite integer and having 3 (an odd number) prime factors.

MATHEMATICA

fQ[n_] := Block[{p = Plus @@ Last /@ FactorInteger@n}, OddQ[p] && p > 1]; Select[ Range@200, fQ[ # ] &] (* Robert G. Wilson v, Jan 04 2006 *)

PROG

(PARI) is(n)=!isprime(n) && bigomega(n)%2 \\ Charles R Greathouse IV, Sep 17 2015

CROSSREFS

Cf. A046340, A046341, A026424.

Sequence in context: A036327 A051144 A067537 * A145784 A014612 A226527

Adjacent sequences:  A046336 A046337 A046338 * A046340 A046341 A046342

KEYWORD

nonn

AUTHOR

Patrick De Geest, Jun 15 1998

STATUS

approved

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Last modified February 20 13:33 EST 2019. Contains 320327 sequences. (Running on oeis4.)