A053357 Numbers k such that 281*2^k + 1 is prime.

1, 7, 9, 11, 33, 81, 113, 143, 185, 227, 359, 393, 631, 1123, 1273, 1351, 3721, 4753, 6617, 9281, 12539, 12961, 19513, 23497, 29695, 33361, 88153, 150751, 448129, 456377, 563713, 612083, 935999, 1041641, 2051865, 2363327

Offset

1,2

Links

Table of n, a(n) for n=1..36.

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

Chris Caldwell, The Prime Pages: 281*2^2051865 + 1 (term that was missed in 2013 and only discovered in 2022)

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[5*10^3], PrimeQ[281*2^# + 1] &] (* G. C. Greubel, May 24 2018 *)

Prog

(PARI) is(n)=ispseudoprime(281*2^n+1) \\ Charles R Greathouse IV, Jun 13 2017
(Magma) [n: n in [1..300] | IsPrime(281*2^n+1)];  // G. C. Greubel, May 24 2018

Crossrefs

Sequence in context: A317633 A259045 A029611 * A029634 A023180 A029474

Adjacent sequences: A053354 A053355 A053356 * A053358 A053359 A053360

Keyword

hard,nonn,more

Author

N. J. A. Sloane, Dec 29 1999

Extensions

a(28)-a(34) from the Ray Ballinger and Wilfrid Keller link by Robert Price, Dec 20 2018

a(35) from Jeppe Stig Nielsen, Apr 04 2020

Missed (due to lack of double checking of calculation results by PrimeGrid in 2013) term 2051865 inserted as new a(35) by Jeppe Stig Nielsen, Mar 08 2022

Status

approved