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

2, 53, 2417

Offset

1,1

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

Links

Table of n, a(n) for n=1..3.

Prog

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

Crossrefs

Primes in A074602.

Sequence in context: A354406 A119777 A176943 * A265443 A234603 A087865

Adjacent sequences: A176943 A176944 A176945 * A176947 A176948 A176949

Keyword

nonn,bref,hard

Author

Vincenzo Librandi, Apr 29 2010

Status

approved