A124621 Numbers k such that 5^k + 4 is prime.
0, 2, 6, 10, 102, 494, 794, 1326, 5242, 5446, 24602, 87606, 188558
Offset: 1
Keywords
Examples
5^2 + 4 = 29 is prime, so 2 is a term.
Links
- F. Firoozbakht, M. F. Hasler, Variations on Euclid's formula for Perfect Numbers, JIS 13 (2010) #10.3.1
Crossrefs
Cf. A059613.
Programs
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Mathematica
Select[Range[0, 2000], PrimeQ[5^# + 4] &] (* Vincenzo Librandi, Oct 01 2012 *)
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PARI
is(n)=ispseudoprime(5^n+4) \\ Charles R Greathouse IV, Feb 17 2017
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
a(13) from Tyler NeSmith, May 04 2021
Comments