A113480 Numbers n such that 17^n + 2 is prime.

0, 1, 105, 369, 25521

Offset: 1

Author

Cino Hilliard, Jan 09 2006

Keywords

• nonn

Comments

Only numbers of the form 6k-5 and 6k-3 need be tested.

No further terms < 100000. - Ray Chandler, Jul 31 2011

a(6) > 2*10^5. - Robert Price, Oct 23 2014

Links

• Henri & Renaud Lifchitz, PRP Records.

Programs

Mathematica

Do[If[PrimeQ[17^n + 2], Print[n]], {n, 0, 2500}] (* Stefan Steinerberger, Jan 28 2006 *)
Join[{0},
Select[Flatten[Table[6 n - {5, 3}, {n, 5000}]], PrimeQ[17^# + 2] &]] (* Harvey P. Dale, Feb 25 2021 *)

PARI

g2(n)= { print1(0","); forstep(x=1,n,6, if(ispseudoprime(17^x+2),print1(x",")); if(ispseudoprime(17^(x+2)+2),print1(x+2",")) ) }

Extensions

25521 from Ray Chandler, Jul 30 2011