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A173144
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Numbers n such that neither prime(n-1) nor prime(n+1) is of form 6k+1.
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1
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2, 4, 6, 8, 14, 16, 25, 27, 29, 31, 34, 40, 42, 44, 50, 53, 55, 56, 61, 63, 65, 70, 78, 80, 82, 88, 90, 93, 95, 97, 103, 108, 117, 119, 125, 127, 136, 138, 141, 143, 145, 147, 149, 151, 153, 155, 157, 159, 161, 163, 165, 172, 177, 183, 185, 191, 193, 195, 200, 207
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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a(1)=2 because prime(2-1)=2 and prime(2+1)=5 are not of form 6k+1.
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MATHEMATICA
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f6kQ[n_]:=And@@(!IntegerQ[(#-1)/6]&/@{Prime[n-1], Prime[n+1]}); Select[ Range[2, 300], f6kQ] (* Harvey P. Dale, Feb 29 2012 *)
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CROSSREFS
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KEYWORD
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nonn,easy,less
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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