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A180744
Numbers k such that 7^k - 5^k - 1 is prime.
0
2, 5, 6, 13, 61, 275, 385, 510, 3559, 9131, 13075, 13829, 28530, 29929, 31555, 39862
OFFSET
1,1
PROG
(Magma) [n: n in [0..500]|IsPrime(7^n-5^n-1)];
(PARI) for(n=1, 10000, if(isprime(7^n-5^n-1), print1(n, ", "))); /* Joerg Arndt, May 15 2011 */
CROSSREFS
Sequence in context: A029544 A058668 A271640 * A092790 A105043 A083095
KEYWORD
nonn,hard,more
AUTHOR
Vincenzo Librandi, Jan 22 2011
EXTENSIONS
a(9)-a(12) from Michael S. Branicky, May 08 2021
a(13)-a(14) from Michael S. Branicky, May 14 2023
a(15)-a(16) from Michael S. Branicky, Oct 27 2024
STATUS
approved