A180744 Numbers k such that 7^k - 5^k - 1 is prime.

2, 5, 6, 13, 61, 275, 385, 510, 3559, 9131, 13075, 13829, 28530, 29929

Offset

1,1

Links

Table of n, a(n) for n=1..14.

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

Adjacent sequences: A180741 A180742 A180743 * A180745 A180746 A180747

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

Status

approved