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A263510
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Numbers n for which the numbers 6n+1, 3n+2, 6n+7 are all odd composite squarefree numbers, but none are semiprimes.
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3
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2121, 3011, 3963, 6125, 7631, 8173, 8275, 8649, 8781, 10519, 10851, 11383, 11599, 11883, 12001, 12163, 12271, 12789, 12807, 13749, 14509, 15381, 15705, 15959, 16583, 16761, 17163, 17473, 17787, 18813, 19283, 19831, 19937, 20483, 20513, 20633, 21673, 22121
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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&;
A263510=Select[Range[10000], Apply[And, Map[CompositeQ[#]&&OddQ[#]&&SquareFreeQ[#]&&(!semiPrimeQ[#])&, {6#+1, 3#+2, 6#+7}]]&]
csnQ[n_]:=Module[{c={6n+1, 3n+2, 6n+7}}, AllTrue[c, CompositeQ]&&AllTrue[ c, SquareFreeQ]&&AllTrue[c, OddQ]&&FreeQ[PrimeOmega[c], 2]]; Select[Range[ 22200], csnQ] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Oct 02 2020 *)
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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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