

A227445


Numbers n such that 7*3^(2*n)+5*3^n+1 is prime.


0



0, 1, 2, 5, 7, 8, 20, 25, 43, 95, 326, 383, 434, 517, 884, 1147, 1303, 2779, 17237, 49867, 81427, 100967
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OFFSET

1,3


COMMENTS

a(23) > 150000.  Robert Price, Apr 05 2015


LINKS

Table of n, a(n) for n=1..22.
Eric L. F. Roettger, A Cubic Extension of the Lucas Functions, Ph. D. Dissertation, Dept. Math. and Statistics, Univ. Calgary, 2009 (see page 196).


MATHEMATICA

Select[Range[0, 3000], PrimeQ[7 3^(2 #) + 5 3^# + 1] &]


PROG

(Magma) [n: n in [0..1000]  IsPrime(7*3^(2*n)+5*3^n+1)]; // Vincenzo Librandi, Apr 06 2015
(PARI) is(n)=ispseudoprime(7*3^(2*n)+5*3^n+1) \\ Charles R Greathouse IV, Jun 13 2017


CROSSREFS

Cf. A058603.
Sequence in context: A188341 A238364 A342730 * A216968 A088757 A308637
Adjacent sequences: A227442 A227443 A227444 * A227446 A227447 A227448


KEYWORD

nonn,more


AUTHOR

Vincenzo Librandi, Jul 14 2013


EXTENSIONS

a(19)a(22) from Robert Price, Apr 05 2015


STATUS

approved



