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A183074
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Prime numbers p such that 2^p - 1 is composite and each of its prime divisors has the form 4j + 3.
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7
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43, 79, 193, 311, 331, 349, 389, 557, 577, 631, 647, 1103
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OFFSET
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1,1
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COMMENTS
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Needed factorizations are in the Cunningham Project.
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LINKS
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FORMULA
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EXAMPLE
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43 is in this sequence because 2^43 - 1 = 431 * 9719 * 2099863, and each of those primes has the form 4j + 3.
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MATHEMATICA
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cQ[n_]:=Module[{x=2^n-1}, !PrimeQ[x]&&Union[Mod[Transpose[ FactorInteger[ x]][[1]], 4]]=={3}]; Select[Prime[Range[120]], cQ] (* Harvey P. Dale, Jun 17 2014 *)
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CROSSREFS
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KEYWORD
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nonn,hard
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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