OFFSET
1,1
COMMENTS
From Daniel Starodubtsev, Aug 03 2019: (Start)
a(5) = 2569^2569 + 4 (8760 digits long).
a(6) > 15000^15000 + 4. (End)
MATHEMATICA
lst={}; Do[p=n^n+4; If[PrimeQ[p], AppendTo[lst, p]], {n, 5!}]; lst (* Vladimir Joseph Stephan Orlovsky, Nov 01 2009 *)
Select[Table[n^n+4, {n, 50}], PrimeQ] (* Harvey P. Dale, Oct 09 2020 *)
PROG
(PARI) f1(n) = for(x=1, n, y=x^x+4; if(ispseudoprime(y), print1(y", ")))
CROSSREFS
KEYWORD
hard,nonn
AUTHOR
Cino Hilliard, Jan 07 2005
STATUS
approved