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A272057
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Numbers n such that 3*4^n - 1 is prime.
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2
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1, 2, 3, 9, 17, 19, 32, 38, 47, 103, 108, 153, 162, 229, 235, 637, 1638, 2102, 2567, 6338, 7449, 12845, 20814, 40165, 61815, 77965, 117380, 207420, 351019, 496350, 600523, 1156367, 2117707, 5742009, 5865925, 5947859
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OFFSET
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1,2
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COMMENTS
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These are Williams primes to base 3.
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LINKS
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[3*4^# - 1] &]
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PROG
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(PARI) for(n=1, 10000, if(isprime(3*4^n-1), print1(n, ", ")))
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CROSSREFS
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Cf. A002235, A000043, A003307, A046865, A079906, A046866, A268061, A268356, A056725, A046867, A079907.
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KEYWORD
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nonn,hard,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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