OFFSET
1,2
COMMENTS
a(13) > 10^5. - Robert Price, Feb 03 2014
a(14) > 2*10^5. - Tyler NeSmith, May 04 2021
LINKS
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, so 2 is a term.
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
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
a(13) from Tyler NeSmith, May 04 2021
STATUS
approved