A301369 Numbers k such that (9^k + 7^k)/16 is prime.

3, 107, 197, 2843, 3571, 4451, 31517, 44819

Offset: 1

Author

Tim Johannes Ohrtmann, Mar 19 2018

Keywords

• nonn
• more
• hard

Comments

All terms are prime.

The corresponding primes are 67, 79401467172644850007356716446663549450843749853576087044440771380676673442288169290888310265443988907, ...

Crossrefs

Cf. A057175, A125956, A211409, A128339, A187819.

Programs

Magma

[n: n in [1..10000] |IsPrime((9^n+7^n)/16)]

Maple

select(n->isprime((9^n+7^n)/16),[seq(n,n=1..10000,2)]); # Muniru A Asiru, Mar 27 2018

Mathematica

Select[Range[1, 10000], PrimeQ[(9^n+7^n)/16] &]

PARI

forprime(n=3, 10000, if(isprime((9^n+7^n)/16), print1(n, ", ")))

Extensions

a(7) from Michael S. Branicky, Apr 29 2023

a(8) from Michael S. Branicky, Jun 22 2024