A059042 Numbers k such that 2*7^k + 5 is prime.

0, 1, 2, 3, 5, 9, 11, 15, 33, 38, 239, 419, 441, 486, 5127, 6953, 6998, 45609

Offset

1,3

Comments

a(18) > 33600. - Jinyuan Wang, Jan 23 2020

Links

Table of n, a(n) for n=1..18.

Mathematica

Do[ If[ PrimeQ[ 2*7^n + 5 ], Print[n] ], {n, 0, 6850} ]

Prog

(PARI) is(n)=ispseudoprime(2*7^n+5) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A157049 A195668 A324698 * A157604 A238657 A329327

Adjacent sequences: A059039 A059040 A059041 * A059043 A059044 A059045

Keyword

nonn,more

Author

Robert G. Wilson v, Feb 12 2001

Extensions

a(16)-a(17) from Jinyuan Wang, Jan 23 2020

a(18) from Michael S. Branicky, Jul 10 2024

Status

approved