A176946 Primes of the form 7^k+2^k.

2, 53, 2417

Offset: 1

Author

Vincenzo Librandi, Apr 29 2010

Keywords

• nonn
• bref
• hard
• changed

Comments

If 7^k+2^k is prime then k is either 0 or a power of 2. The corresponding values of k for a(1)-a(3) are 0, 2 and 4. If it exists, a(4) has k = 2^m with m > 19, and therefore it is larger than 7^(2^20) > 10^886149. - Amiram Eldar, Jul 17 2025

Crossrefs

Primes in A074602.

Programs

Magma

[ a: k in [0..2100] | IsPrime(a) where a is 7^k+2^k ];