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A056956
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Numbers n such that 6n+1 and 6n+5 are both primes.
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12
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1, 2, 3, 6, 7, 11, 13, 16, 17, 18, 21, 27, 32, 37, 38, 46, 51, 52, 58, 63, 66, 73, 76, 77, 81, 83, 102, 107, 112, 123, 126, 128, 137, 142, 143, 146, 147, 151, 156, 161, 168, 181, 182, 202, 213, 216, 217, 237, 238, 241, 247, 248, 258, 261, 263, 266, 268, 277, 282
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OFFSET
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1,2
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COMMENTS
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Note that if prime p>3 then p mod 6 = 1 or 5.
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LINKS
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FORMULA
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EXAMPLE
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a(2)=2 since 6*2+1=13 and 6*2+5=17 are both prime.
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MATHEMATICA
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Select[Range[300], And @@ PrimeQ /@ ({1, 5} + 6#) &] (* Ray Chandler, Jun 29 2008 *)
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PROG
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(PARI) is(n)=isprime(n*6+1)&&isprime(n*6+5) \\ M. F. Hasler, Apr 05 2017
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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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