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A242017
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Smallest prime factor of composites in the sequence A000051(n) = 2^n+1.
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2
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3, 3, 5, 3, 3, 5, 3, 17, 3, 5, 3, 3, 5, 3, 17, 3, 5, 3, 97, 3, 5, 3, 17, 3, 5, 3, 641, 3, 5, 3, 17, 3, 5, 3, 257, 3, 5, 3, 17, 3, 5, 3, 193, 3, 5, 3, 17, 3, 5, 3, 257, 3, 5, 3, 17, 3, 5, 3, 274177, 3, 5, 3
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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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FactorInteger[#][[1, 1]]&/@Select[(2^Range[70]+1), CompositeQ] (* Harvey P. Dale, Feb 17 2017 *)
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PROG
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(PARI) for(n=1, 1e2, if(!ispseudoprime(2^n+1), p=factor(2^n+1)[1, 1]; print1(p, ", ")))
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CROSSREFS
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KEYWORD
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nonn,changed
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AUTHOR
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STATUS
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approved
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