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A178996
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Numbers n such that 5^n mod 2^n is prime.
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0
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3, 10, 19, 24, 28, 61, 79, 96, 104, 125, 132, 191, 196, 243, 292, 302, 462, 466, 586, 621, 1508, 3307, 3823, 4729, 5370, 6721, 8110, 11145, 13502, 13762, 20266, 27868, 38522, 75470
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OFFSET
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1,1
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COMMENTS
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Here 'mod' denotes the binary modulo operation (nonnegative remainder).
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LINKS
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MATHEMATICA
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fQ[n_] := PrimeQ@ PowerMod[5, n, 2^n]; k = 1; lst = {}; While[k < 17501, If[fQ@ k, AppendTo[lst, k]]; k++]; lst
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PROG
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(PARI) for(n=1, 9999, ispseudoprime(5^n % 2^n) & print1(n", ")) \\ M. F. Hasler, Jan 03 2011
(PARI) for(n=1, 1e5, if(ispseudoprime(lift(Mod(5, 2^n)^n)), print1(n", "))) \\ Charles R Greathouse IV, Oct 10 2011
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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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