1,1

Note that if n > 2 and n+1 is prime then (by Fermat's theorem) n+1 divides 3^n+n.

Do[ If[ PrimeQ[ 3^n + n ], Print[ n ] ], {n, 0, 3000} ]

v={2}; Do[If[EvenQ[n]&&Mod[n, 3]!=0&&!PrimeQ[n+1]&&PrimeQ[3^n+n], v=Append[v, n]; Print[v]], {n, 3, 19000}]

Sequence in context: A126328 A013026 A121789 this_sequence A116618 A037723 A037618

Adjacent sequences: A057897 A057898 A057899 this_sequence A057901 A057902 A057903

nonn

Robert G. Wilson v (rgwv(AT)rgwv.com), Nov 16 2000

18248 from Farideh Firoozbakht (f.firoozbakht(AT)sci.ui.ac.ir), Aug 21 2003