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A033992
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Numbers that are divisible by exactly three different primes.
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17
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30, 42, 60, 66, 70, 78, 84, 90, 102, 105, 110, 114, 120, 126, 130, 132, 138, 140, 150, 154, 156, 165, 168, 170, 174, 180, 182, 186, 190, 195, 198, 204, 220, 222, 228, 230, 231, 234, 238, 240, 246, 252, 255, 258, 260, 264, 266, 270, 273, 276, 280, 282, 285
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Below 210, A000977 and this sequence are identical.
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..1000
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FORMULA
| omega(a(n)) = A001221(a(n)) = 3. - Jonathan Vos Post (jvospost3(AT)gmail.com), Sep 20 2005
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EXAMPLE
| 220=2*2*5*11 is here but 210 is not; compare A000977.
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MAPLE
| A033992 := proc(n)
if (nops(numtheory[factorset](n)) = 3) then
RETURN(n)
fi: end: seq(A033992(n), n=1..500); # - Jani Melik, Feb 24 2011
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MATHEMATICA
| Select[Range[0, 6! ], Length[FactorInteger[ # ]]==3&] [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Apr 22 2010]
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CROSSREFS
| Cf. A000977, A007774, A000961, A033993, A051270.
Cf. A112802.
Sequence in context: A090800 A114816 A000977 * A091454 A175727 A179945
Adjacent sequences: A033989 A033990 A033991 * A033993 A033994 A033995
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu)
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