A193177 Numbers k such that 2*17^k - 1 is prime.

2, 30, 74, 122, 386, 476, 630, 20132

Offset

1,1

Comments

Is it true that a(n)= 0 or 2 (mod 6) and a(n)= 0 or 2 (mod 4)?

Yes. This can be proved mod 21. [Charles R Greathouse IV, Jul 31 2011]

Links

Table of n, a(n) for n=1..8.

Mathematica

Table[If[PrimeQ[2*17^m-1], m], {m, 1, 2000}]//Union

Prog

(PARI) forstep(n=2, 1e4, [4, 2], if(ispseudoprime(2*17^n-1), print1(n", "))) \\ Charles R Greathouse IV, Jul 31 2011

Crossrefs

Sequence in context: A244379 A189100 A085637 * A157870 A285991 A078838

Adjacent sequences: A193174 A193175 A193176 * A193178 A193179 A193180

Keyword

nonn,more

Author

José María Grau Ribas, Jul 17 2011

Extensions

a(8) from Michael S. Branicky, Jul 14 2023

Status

approved