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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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified December 6 09:25 EST 2022. Contains 358608 sequences. (Running on oeis4.)