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A105441
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Numbers with at least two odd prime factors (not necessarily distinct).
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6
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9, 15, 18, 21, 25, 27, 30, 33, 35, 36, 39, 42, 45, 49, 50, 51, 54, 55, 57, 60, 63, 65, 66, 69, 70, 72, 75, 77, 78, 81, 84, 85, 87, 90, 91, 93, 95, 98, 99, 100, 102, 105, 108, 110, 111, 114, 115, 117, 119, 120, 121, 123, 125, 126, 129, 130, 132, 133, 135, 138, 140, 141
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Complement of A093641; A087436(a(n)) > 1; A093642 is a subsequence.
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LINKS
| Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
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MATHEMATICA
| opf3Q[n_]:=Count[Flatten[Table[First[#], {Last[#]}]&/@FactorInteger[n]], _?OddQ]>1 (* From Harvey P. Dale, Jun 13 2011 *)
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PROG
| (PARI) upTo(lim)=my(v=List(), p=7, m); forprime(q=8, lim, forstep(n=p+2, q-2, 2, m=n; while(m<=lim, listput(v, m); m<<=1)); p=q); forstep(n=p+2, lim, 2, listput(v, n)); vecsort(Vec(v)) \\ Charles R Greathouse IV, Aug 08 2011
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CROSSREFS
| Sequence in context: A037002 A071149 A110473 * A093642 A177733 A118236
Adjacent sequences: A105438 A105439 A105440 * A105442 A105443 A105444
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KEYWORD
| nonn,easy
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AUTHOR
| Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Apr 09 2005
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