A216889 Numbers k such that 12*3^k + 1 is prime.

0, 1, 2, 5, 13, 14, 38, 200, 248, 884, 1004, 1253, 1634, 3305, 3521, 9601, 19784, 72697

Offset

1,3

Comments

a(19) > 2*10^5. - Robert Price, Mar 16 2014

All terms are verified primes (i.e., not merely probable primes). - Robert Price, Mar 16 2014

Links

Table of n, a(n) for n=1..18.

Formula

a(n) = A005537(n+1) - 1. - Bruno Berselli, Sep 27 2012

Mathematica

Select[Range[4000], PrimeQ[12 * 3^# + 1] &]

Prog

(Magma) [n: n in [0..4000] | IsPrime(12*3^n + 1)];
(PARI) is(n)=ispseudoprime(12*3^n+1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A003306, A005537-A005539, A056805.

Sequence in context: A247543 A220268 A049476 * A334494 A168486 A038914

Adjacent sequences: A216886 A216887 A216888 * A216890 A216891 A216892

Keyword

nonn,more

Author

Vincenzo Librandi, Sep 26 2012

Extensions

a(16)-a(17) from Vincenzo Librandi, Sep 30 2012

a(18) from Robert Price, Mar 16 2014

Status

approved