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A137770
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Prime numbers p such that p +- ((p-1)/7) are primes.
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1
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211, 673, 883, 1093, 1303, 2731, 7561, 8443, 10711, 13063, 14323, 15373, 16843, 18523, 24571, 30703, 31081, 31963, 36541, 36583, 40111, 41161, 42043, 43051, 44563, 44773, 55441, 63421, 64891, 65563, 67411, 68041, 70393, 71233, 74551, 75391, 79843
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OFFSET
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1,1
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LINKS
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EXAMPLE
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211+-30 = primes;
673+-(672/7) = primes.
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MATHEMATICA
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w=7; s=""; For[i=1, i<10^3*2, p=Prime[i]; If[PrimeQ[p-((p-1)/w)]&&PrimeQ[p+((p-1)/w)], (*Print[p, ":", p-((p-1)/w), ", ", p+((p-1)/w)]; *)s=s<>ToString[p]<>", "]; i++ ]; Print[s]
Select[Prime[Range[80000]], PrimeQ[# + (# - 1) / 7] && PrimeQ[# - (# - 1) / 7] &] (* Vincenzo Librandi, Jun 15 2013 *)
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PROG
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(Magma) [p: p in PrimesInInterval(5, 80000)| IsPrime((8*p-1) div 7 ) and IsPrime((6*p+1) div 7)]; // Vincenzo Librandi, Jun 15 2013
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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