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A264779
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Numbers n for which the numbers 6n+1, 3n+2, 6n+7 are all odd composite squarefree, but not all semiprimes.
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4
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183, 249, 361, 371, 413, 459, 487, 501, 515, 525, 609, 613, 639, 697, 749, 763, 795, 823, 893, 911, 931, 1009, 1043, 1051, 1081, 1093, 1213, 1237, 1263, 1271, 1275, 1301, 1373, 1383, 1393, 1399, 1425, 1509, 1513, 1523, 1543, 1561, 1581, 1589, 1617, 1659, 1663
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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semiPrimeQ:=Last[Total[FactorInteger[#]]]==2&;
A264779=Select[Range[1000], Map[Apply[And, #]&, Transpose[Map[{CompositeQ[#], OddQ[#], SquareFreeQ[#], semiPrimeQ[#]}&, {6#+1, 3#+2, 6#+7}]]]=={True, True, True, False}&]
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PROG
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(PARI) is(n)={bittest(n, 0)&&Set(apply(issquarefree, n=[3*n+2, 6*n+1, 6*n+7]))==[1]&&vecmax(n=apply(omega, n))>2&&vecmin(n)>1} \\ M. F. Hasler, Nov 25 2015
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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