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A059613
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Numbers n such that 5^n-4 is prime.
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6
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5, 7, 15, 47, 81, 115, 267, 285, 7641, 19089, 25831, 32115, 59811, 70155
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OFFSET
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1,1
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COMMENTS
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a(15) > 10^5. - Robert Price, Feb 03 2014
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LINKS
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Table of n, a(n) for n=1..14.
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EXAMPLE
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81 is present because 5^81-4 is prime.
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MATHEMATICA
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Select[Range[10000], PrimeQ[5^# - 4] &] (* Vincenzo Librandi, Oct 03 2012 *)
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PROG
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(PARI) is(n)=ispseudoprime(5^n-4) \\ Charles R Greathouse IV, Feb 20 2017
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CROSSREFS
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Sequence in context: A076860 A283592 A067589 * A242503 A116048 A120282
Adjacent sequences: A059610 A059611 A059612 * A059614 A059615 A059616
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KEYWORD
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nonn,hard,more
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AUTHOR
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Andrey V. Kulsha, Feb 07 2001
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EXTENSIONS
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a(10)-a(14) from Robert Price, Feb 03 2014
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STATUS
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approved
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