%I #15 Oct 30 2017 03:52:07
%S 3,7,23,29,59,1249,1709,1823,1931,3433,8863,43201,78707
%N Numbers n such that (25^n+1)/26 is a prime.
%C Some of the larger terms may only correspond to probable primes.
%C a(14) > 10^5. - _Robert Price_, Jun 10 2013
%H H. Dubner and T. Granlund, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL3/DUBNER/dubner.html">Primes of the Form (b^n+1)/(b+1)</a>, J. Integer Sequences, 3 (2000), #P00.2.7.
%t Select[Range[0, 2000], PrimeQ[(25^# + 1) / 26] &] (* _Vincenzo Librandi_, Oct 29 2017 *)
%o (PARI) isok(n) = (denominator(p=(25^n+1)/26)==1) && isprime(p); \\ _Michel Marcus_, Oct 29 2017
%K nonn,more
%O 1,1
%A _N. J. A. Sloane_, Sep 15 2000
%E a(12)-a(13) from _Robert Price_, Jun 10 2013
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