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A059613 Numbers n such that 5^n-4 is prime. 6
5, 7, 15, 47, 81, 115, 267, 285, 7641, 19089, 25831, 32115, 59811, 70155 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(15) > 10^5. - Robert Price, Feb 03 2014

LINKS

Table of n, a(n) for n=1..14.

EXAMPLE

81 is present because 5^81-4 is prime.

MATHEMATICA

Select[Range[10000], PrimeQ[5^# - 4] &] (* Vincenzo Librandi, Oct 03 2012 *)

PROG

(PARI) is(n)=ispseudoprime(5^n-4) \\ Charles R Greathouse IV, Feb 20 2017

CROSSREFS

Sequence in context: A076860 A283592 A067589 * A242503 A116048 A120282

Adjacent sequences:  A059610 A059611 A059612 * A059614 A059615 A059616

KEYWORD

nonn,hard,more

AUTHOR

Andrey V. Kulsha, Feb 07 2001

EXTENSIONS

a(10)-a(14) from Robert Price, Feb 03 2014

STATUS

approved

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Last modified July 6 23:56 EDT 2020. Contains 335484 sequences. (Running on oeis4.)