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A124621 Numbers n such that 5^n+4 is prime. 7
0, 2, 6, 10, 102, 494, 794, 1326, 5242, 5446, 24602, 87606 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(13) > 10^5. - Robert Price, Feb 03 2014

LINKS

Table of n, a(n) for n=1..12.

F. Firoozbakht, M. F. Hasler, Variations on Euclid's formula for Perfect Numbers, JIS 13 (2010) #10.3.1

EXAMPLE

5^2+4=29 is prime

MATHEMATICA

Select[Range[0, 2000], PrimeQ[5^# + 4] &] (* Vincenzo Librandi, Oct 01 2012 *)

PROG

(PARI) is(n)=ispseudoprime(5^n+4) \\ Charles R Greathouse IV, Feb 17 2017

CROSSREFS

Cf. A059613.

Sequence in context: A322756 A048782 A083458 * A325237 A065799 A162582

Adjacent sequences:  A124618 A124619 A124620 * A124622 A124623 A124624

KEYWORD

nonn

AUTHOR

Artur Jasinski, Dec 21 2006

EXTENSIONS

Added the first term 0 by Vincenzo Librandi, Oct 01 2012

a(9) - a(10) from Bruno Berselli, Aug 12 2013

a(11)-a(12) from Robert Price, Feb 03 2014

STATUS

approved

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Last modified June 16 05:18 EDT 2019. Contains 324145 sequences. (Running on oeis4.)