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Numbers k such that 13^k + 4 is prime.
3

%I #18 May 10 2021 02:32:44

%S 0,1,2,6,10,15,94,198,219,4543,11511,12638,45606

%N Numbers k such that 13^k + 4 is prime.

%C a(14) > 10^5. - _Tyler NeSmith_, May 09 2021

%H Henri Lifchitz and Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=13%5En%2B4">PRP Records</a>.

%o (PARI) for(n=0,300,if(isprime(13^n+4),print1(n",")))

%K hard,more,nonn

%O 1,3

%A _Jason Earls_, Mar 08 2008

%E a(13) from Lelio R. Paula contributed by _Iain Fox_, Nov 24 2017