OFFSET
1,1
COMMENTS
Some of the larger terms may only correspond to probable primes.
a(11) > 10^5. - Robert Price, Jul 10 2013
LINKS
H. Dubner and T. Granlund, Primes of the Form (b^n+1)/(b+1), J. Integer Sequences, 3 (2000), #P00.2.7.
H. Lifchitz, Mersenne and Fermat primes field
MATHEMATICA
Select[Range[3000], PrimeQ[(30^# + 1) / 31] &] (* Vincenzo Librandi, Oct 29 2017 *)
PROG
(PARI) isok(n) = (denominator(p=(30^n+1)/31)==1) && isprime(p); \\ Michel Marcus, Oct 29 2017
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Rick L. Shepherd, May 22 2002
EXTENSIONS
a(8) from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008
a(9)-a(10) from Robert Price, Jul 10 2013
STATUS
approved