OFFSET
1,1
COMMENTS
Farideh Firoozbakht reports that the only known prime of the form 5^n + n occurs when n = 7954 and that there are no others up to 20200. Oct 11 2003.
a(7) > 2*10^5. - Robert Price, Jan 16 2014
MATHEMATICA
Do[ If[ PrimeQ[ 5^n - n ], Print[ n ] ], {n, 1, 13400} ]
PROG
(PARI) is(n)=ispseudoprime(5^n-n) \\ Charles R Greathouse IV, Feb 20 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Nov 17 2000
EXTENSIONS
The sixth term was found by Farideh Firoozbakht, who reports that there are no others up to 13400, Oct 11 2003
STATUS
approved