A181141 Numbers k such that (8^k + 7^k)/15 is prime.

7, 13, 31, 43, 269, 353, 383, 619, 829, 877, 4957, 5711, 8317, 21739, 24029, 38299

Offset: 1

Author

Jean-Louis Charton, Oct 06 2010

Keywords

• hard
• nonn

Comments

Terms 21739 and 24029 were found by Lelio R. Paula in February and April 2009. Term 38299 was found by Jean-Louis Charton in October 2010 corresponding to a probable prime with 34587 digits.

a(17) > 10^5. - Robert Price, Dec 29 2012

Links

• Top probable primes of form (8^n+7^n)/15

Crossrefs

See also A062574.

Programs

PARI

is(n)=isprime((8^n+7^n)/15) \\ Charles R Greathouse IV, Feb 17 2017