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A050539
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Numbers k such that 27*2^k-1 is prime.
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5
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1, 2, 4, 5, 8, 10, 14, 28, 37, 38, 70, 121, 122, 160, 170, 253, 329, 362, 454, 485, 500, 574, 892, 962, 1213, 1580, 2642, 2708, 4505, 8152, 11858, 13300, 15041, 16118, 16778, 19069, 22769, 29020, 30298, 30377, 35942, 42817, 42869, 62024, 74629, 90449, 91042, 117901, 128594, 143330, 152530, 157898, 175852, 340682, 444622, 627794, 729314, 777992, 1108214, 1163629, 1253870
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OFFSET
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1,2
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COMMENTS
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3855094, 4542344 and 4583717 are also in the sequence. - Felix Fröhlich, Sep 19 2014
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LINKS
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MATHEMATICA
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For[n = 1, n <= 10000, n++, If[PrimeQ[27*2^n - 1], Print[n]]] (* Wesley Ivan Hurt, May 19 2014 *)
Select[Range[1000], PrimeQ[27*2^# - 1] & ] (* Robert Price, Dec 22 2018 *)
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PROG
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(PARI) a(n)=if(ispseudoprime(27*2^n-1), print1(n, ", ")) \\ Felix Fröhlich, Sep 19 2014
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CROSSREFS
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KEYWORD
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hard,nonn
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AUTHOR
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EXTENSIONS
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More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
a(59)-a(61) from the Wilfrid Keller link by Robert Price, Dec 22 2018
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STATUS
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approved
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