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 #21 Aug 27 2022 03:16:53
%S 0,1,2,5,13,14,38,200,248,884,1004,1253,1634,3305,3521,9601,19784,
%T 72697
%N Numbers k such that 12*3^k + 1 is prime.
%C a(19) > 2*10^5. - _Robert Price_, Mar 16 2014
%C All terms are verified primes (i.e., not merely probable primes). - _Robert Price_, Mar 16 2014
%F a(n) = A005537(n+1) - 1. - _Bruno Berselli_, Sep 27 2012
%t Select[Range[4000], PrimeQ[12 * 3^# + 1] &]
%o (Magma) [n: n in [0..4000] | IsPrime(12*3^n + 1)];
%o (PARI) is(n)=ispseudoprime(12*3^n+1) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y Cf. A003306, A005537-A005539, A056805.
%K nonn,more
%O 1,3
%A _Vincenzo Librandi_, Sep 26 2012
%E a(16)-a(17) from _Vincenzo Librandi_, Sep 30 2012
%E a(18) from _Robert Price_, Mar 16 2014