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A059803
Numbers n such that 9^n - 8^n is prime or a strong pseudoprime.
13
2, 7, 29, 31, 67, 149, 401, 2531, 19913, 30773, 53857, 170099
OFFSET
1,1
COMMENTS
Some of the larger entries may only correspond to probable primes.
In general, for any positive integers n, a and b, a>b, a necessary condition for a^n-b^n to be prime is that either a-b=1 and n be a prime or n=1 and a-b be prime (from Arturo Magidin and Hagman in Sci.Math, Sep 11, 2010). - Vincenzo Librandi, Sep 12 2010
PROG
(PARI) is(n)=ispseudoprime(9^n-8^n) \\ Charles R Greathouse IV, Jun 13 2017
KEYWORD
nonn,hard
AUTHOR
Mike Oakes, Feb 23 2001
EXTENSIONS
Three more terms found by Jean-Louis Charton in 2004-2005: a(9) = 30773, a(10) = 53857, a(11) = 170099. - Alexander Adamchuk, Dec 08 2006
STATUS
approved