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A217381 Numbers n such that 8^n + 7 is prime. 1
2, 6, 10, 26, 42, 58, 68, 196, 266, 602, 1170, 1288, 1290, 2990, 4110, 6292, 7446, 36928, 57490, 65478, 78570, 188832 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All terms are equal to 1/3 of the multiples of 3 in A057195.

Naturally these numbers are even because (9-1)^(2n+1)+7 is divisible by 3. - Bruno Berselli, Oct 03 2012

LINKS

Table of n, a(n) for n=1..22.

MATHEMATICA

Select[Range[10000], PrimeQ[8^# + 7] &]

PROG

(PARI) is(n)=ispseudoprime(8^n+7) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

Cf. A057195, A217354, A217355.

Cf. A144360 (associated primes).

Sequence in context: A079713 A055237 A057434 * A162581 A061547 A218791

Adjacent sequences:  A217378 A217379 A217380 * A217382 A217383 A217384

KEYWORD

nonn

AUTHOR

Vincenzo Librandi, Oct 02 2012

EXTENSIONS

a(18)-a(22) from A057195 by Robert Price, Jul 23 2017

STATUS

approved

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Last modified December 12 22:06 EST 2019. Contains 329963 sequences. (Running on oeis4.)