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

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

Offset: 1

Author

José María Grau Ribas, Jul 17 2011

Keywords

• nonn
• more

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]

Programs

Mathematica

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

PARI

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

Extensions

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