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A168626
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Numbers n such that n and n+-1 have 3 or more distinct prime factors.
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4
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645, 741, 805, 987, 1035, 1065, 1105, 1221, 1275, 1309, 1310, 1463, 1495, 1581, 1749, 1885, 1886, 1925, 1989, 2014, 2015, 2109, 2135, 2211, 2255, 2261, 2289, 2295, 2331, 2355, 2365, 2379, 2409, 2465, 2485, 2541, 2584, 2585, 2665, 2666, 2667, 2679, 2685
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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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f[n_]:=Length[FactorInteger[n]]; lst={}; Do[If[f[n]>=3&&f[n-1]>=3&&f[n+1]>=3, AppendTo[lst, n]], {n, 7!}]; lst
Mean/@SequencePosition[Table[If[PrimeNu[n]>2, 1, 0], {n, 2700}], {1, 1, 1}] (* The program uses the SequencePosition function from Mathematica version 10 *) (* Harvey P. Dale, Jun 05 2016 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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