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A062586
Numbers k such that 20^k - 19^k is prime.
1
5, 17, 109, 1979, 6899, 7331, 18661, 79621, 81649
OFFSET
1,1
COMMENTS
Terms k > 1000 may correspond to (unproven) strong pseudoprimes.
PROG
(PARI) is(n)=ispseudoprime(20^n-19^n) \\ Charles R Greathouse IV, Jun 12 2017
KEYWORD
nonn,hard
AUTHOR
Mike Oakes, May 18 2001, May 19 2001
EXTENSIONS
a(7)-a(9) found by Jean-Louis Charton in February and March 2011
Edited by M. F. Hasler, Sep 16 2013
STATUS
approved