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URL: https://oeis.org/A217380

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A217380
Numbers k such that 8^k - 7 is prime.
1
13, 661, 773, 833, 4273, 40613, 302913
OFFSET
1,1
COMMENTS
All terms are equal to 1/3 of the multiples of 3 in A059609.
Naturally these numbers are odd since (9-1)^(2n)-7 is divisible by 3. - Bruno Berselli, Oct 04 2012
MATHEMATICA
Select[Range[4000], PrimeQ[8^# - 7] &]
PROG
(PARI) is(n)=ispseudoprime(8^n-7) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Vincenzo Librandi, Oct 02 2012
EXTENSIONS
a(7) using A059609 from Michael S. Branicky, Sep 15 2024
STATUS
approved