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A216889 Numbers n such that 12*3^n + 1 is prime. 1
0, 1, 2, 5, 13, 14, 38, 200, 248, 884, 1004, 1253, 1634, 3305, 3521, 9601, 19784, 72697 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

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

All terms are verified primes (ie, not 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 * A168486 A038914 A019419

Adjacent sequences:  A216886 A216887 A216888 * A216890 A216891 A216892

KEYWORD

nonn

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

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Last modified January 19 18:13 EST 2020. Contains 331051 sequences. (Running on oeis4.)