A114301 - OEIS

%I #20 Jun 05 2024 01:23:16

%S 1,3,19,1013,4133,9833,30809,64459

%N Numbers k such that 2^k + 3^k + 5^k + 7^k is a prime number.

%C All terms are odd. - _Robert Israel_, May 03 2018

%e 2^3 + 3^3 + 5^3 + 7^3 = 503 (prime), thus 3 is in the sequence.

%p select(t -> isprime(2^t+3^t+5^t+7^t), [seq(i,i=1..10000,2)]); # _Robert Israel_, May 03 2018

%t Do[If[PrimeQ[2^n+3^n+5^n+7^n], Print[n]], {n,1,5000}]

%Y Cf. A135168.

%K hard,more,nonn

%O 1,2

%A _Stefan Steinerberger_, Feb 05 2006

%E a(6) from _Ryan Propper_, Mar 24 2006

%E a(7) from Joao Carlos Leandro da Silva (zxawyh66(AT)yahoo.com), Jun 01 2009

%E a(8) from _Michael S. Branicky_, Jun 04 2024