Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #23 Dec 09 2024 14:20:37
%S 0,1,2,5,11,28,65,72,361,479,494,599,1062,1094,1193,2827,3271,3388,
%T 3990,4418,11178,16294,25176,42500,68320,85698,145259,159119,169771,
%U 252665,412051
%N Numbers k such that 6*5^k - 1 is prime.
%C All terms correspond to verified primes, that is, not merely probable primes.
%t Select[Range[0, 10000], PrimeQ[6*5^# - 1] &]
%o (Magma) [n: n in [0..2*10^3] | IsPrime(6*5^n-1)]; // _Vincenzo Librandi_, May 09 2015
%o (PARI) is(n)=ispseudoprime(6*5^n-1) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y Cf. A143279.
%K nonn,hard,more
%O 1,3
%A _Robert Price_, May 08 2015
%E a(30) from _Riley Fisher_, Sep 20 2024
%E a(31) from _Riley Fisher_, Dec 09 2024