A032485 Numbers k such that 217*2^k+1 is prime.

66, 84, 880, 3344, 4440, 10148, 18084, 18210, 28380, 35296, 335826, 546500, 570616, 624208, 670496, 1690664, 2264546

Offset

1,1

Links

Table of n, a(n) for n=1..17.

Ray Ballinger, Proth Search Page

Ray Ballinger and Wilfrid Keller, List of primes k.2^n + 1 for k < 300

Wilfrid Keller, List of primes k.2^n - 1 for k < 300

Index entries for sequences of n such that k*2^n-1 (or k*2^n+1) is prime

Mathematica

Select[Range[1000], PrimeQ[217*2^# + 1] & ] (* Robert Price, Dec 19 2018 *)

Prog

(PARI) is(n)=ispseudoprime(217*2^n+1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A109750 A127654 A293175 * A257029 A223734 A031411

Adjacent sequences: A032482 A032483 A032484 * A032486 A032487 A032488

Keyword

nonn,hard,more

Author

N. J. A. Sloane.

Extensions

a(11)-a(16) from the Ray Ballinger and Wilfrid Keller link by Robert Price, Dec 19 2018

a(17) from Jeppe Stig Nielsen, Apr 04 2020

Status

approved