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A216888
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Numbers n such that 6*3^n + 1 is prime.
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0
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0, 1, 3, 4, 5, 8, 15, 16, 29, 53, 56, 59, 64, 131, 179, 319, 695, 781, 821, 896, 1251, 1453, 4216, 5479, 6224, 7841, 12095, 13781, 17719, 43955, 64821, 82779, 105105, 152528, 165895, 191813, 529679, 1074725, 1086111, 1175231
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OFFSET
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1,3
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LINKS
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FORMULA
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EXAMPLE
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3 is in the sequence because 6*3^3 + 1 = 163 is prime;
7 is not in the sequence because 6*3^7 + 1 = 13123 = 11*1193 is composite.
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MATHEMATICA
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Select[Range[5000], PrimeQ[6 3^# + 1] &]
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PROG
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(Magma) /* Gives only the terms up to 1453: */ [n: n in [0..1500] | IsPrime(6*3^n + 1)];
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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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