OFFSET
1,1
COMMENTS
Numbers n such that (2^n + 3^n)/5 is prime are listed in A057469 = {3, 7, 11, 83, 149, 223, 599, 647, 1373, 8423, ...}.
MATHEMATICA
Do[f=(2^n+3^n)/5; If[PrimeQ[f], Print[{n, f}]], {n, 1, 1000}]
Select[Table[(3^n+2^n)/5, {n, 500}], PrimeQ] (* Harvey P. Dale, Aug 07 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Alexander Adamchuk, Feb 05 2007
STATUS
approved