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A023256
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Primes that remain prime through 2 iterations of function f(x) = 6x + 1.
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3
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2, 17, 47, 61, 101, 131, 151, 331, 367, 461, 607, 751, 937, 971, 1151, 1321, 1327, 1361, 1481, 1511, 1607, 1811, 1847, 1907, 2081, 2287, 2347, 2357, 2791, 2851, 2971, 3251, 3257, 3457, 3491, 3581, 3761, 4007, 4091, 4127, 4861, 4967, 5231, 5347, 5387, 5407
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OFFSET
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1,1
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COMMENTS
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Primes p such that 6*p+1 and 36*p+7 are also primes. - Vincenzo Librandi, Aug 04 2010
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LINKS
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FORMULA
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a(n) == 1 or 7 (mod 10) for n > 1. - John Cerkan, Sep 14 2016
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MATHEMATICA
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Select[Prime[Range[800]], AllTrue[Rest[NestList[6#+1&, #, 2]], PrimeQ]&] (* Harvey P. Dale, Oct 17 2020 *)
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PROG
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(Magma) [n: n in [0..100000] | IsPrime(n) and IsPrime(6*n+1) and IsPrime(36*n+7)] // Vincenzo Librandi, Aug 04 2010
(PARI) lista(nn) = forprime(n=1, nn, if (isprime(p=6*n+1) && isprime(6*p+1), print1(n, ", "))); \\ Michel Marcus, Oct 17 2015
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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