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A217380

Numbers k such that 8^k - 7 is prime.

13, 661, 773, 833, 4273, 40613, 302913

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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

LINKS

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,changed

AUTHOR

EXTENSIONS

a(7) using A059609 from Michael S. Branicky, Sep 15 2024

STATUS

approved