A180740 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A180740

Numbers k such that 7^k + 5^k + 1 is prime.

%I #21 Oct 12 2024 01:40:02

%S 0,1,11,731,3029,63071

%N Numbers k such that 7^k + 5^k + 1 is prime.

%o (Magma) [n: n in [0..700]|IsPrime(7^n+5^n+1)];

%o (PARI) is(n)=ispseudoprime(7^n+5^n+1) \\ _Charles R Greathouse IV_, Jun 13 2017

%K nonn,more

%O 1,3

%A _Vincenzo Librandi_, Jan 22 2011

%E a(4)-a(5) from _D. S. McNeil_, Jan 24 2011

%E a(6) from _Michael S. Branicky_, Oct 11 2024