A104065 Primes of the form 7^k + 4.

5, 11, 53, 347, 16811, 823547, 40353611, 678223072853, 27368747340080916347

Offset: 1

Author

Roger L. Bagula, Mar 02 2005

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..16

Crossrefs

Cf. A096305.

Programs

Mathematica

a = Delete[Union[Flatten[Table[If [PrimeQ[7^n + 3 + 1] == True, 7^n + 3 + 1, 0], {n, 1, 400}]]], 1]
Select[7^Range[0,30]+4,PrimeQ] (* Harvey P. Dale, Jul 31 2021 *)

Formula

a(n) = 7^A096305(n) + 4. - Amiram Eldar, Jun 05 2025

Extensions

Initial 5 from Vincenzo Librandi, Dec 10 2010