A181979 - OEIS

%I #16 Mar 14 2016 03:30:23

%S 5,151,3719,49211,77237

%N Numbers n such that (29^n - 1)/28 is prime.

%H H. Dubner, <a href="http://dx.doi.org/10.1090/S0025-5718-1993-1185243-9">Generalized repunit primes</a>, Math. Comp., 61 (1993), 927-930.

%H H. Lifchitz, <a href="http://www.primenumbers.net/Henri/us/MersFermus.htm">Mersenne and Fermat primes field</a>

%H <a href="/index/Pri#primepop">Index to primes in various ranges</a>, form ((k+1)^n-1)/k

%t Select[Prime[Range[100000]], PrimeQ[(29^#-1)/28]&]

%o (PARI) isok(n) = isprime((29^n-1)/28); \\ _Michel Marcus_, Mar 13 2016

%K hard,more,nonn

%O 1,1

%A _Robert Price_, Apr 04 2012