A032356 Numbers k such that 13*2^k+1 is prime.
2, 8, 10, 20, 28, 82, 188, 308, 316, 1000, 28280, 38008, 43856, 88018, 109258, 114296, 521306, 562456, 684560, 1038896, 1499876, 1861732, 4998362, 5523860, 6481780, 8989858
Offset: 1
Links
- Ray Ballinger, Proth Search Page
- Ray Ballinger and Wilfrid Keller, List of primes k.2^n + 1 for k < 300
- Y. Gallot, Proth.exe: Windows Program for Finding Large Primes
- 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
Crossrefs
Cf. A002257.
Programs
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Mathematica
Select[Range[1000], PrimeQ[13*2^#+1] &] (* Amiram Eldar, Dec 12 2018 *)
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PARI
is(n)=ispseudoprime(13*2^n+1) \\ Charles R Greathouse IV, May 22 2017
Extensions
Added more terms (from http://web.archive.org/web/20161028080239/http://www.prothsearch.net/riesel.html), Joerg Arndt, Apr 07 2013
a(23) from http://www.prothsearch.com/riesel1.html by Robert Price, Dec 12 2018
a(24) from Jeppe Stig Nielsen, Jan 24 2020
a(25)-a(26) from Jeppe Stig Nielsen, Dec 21 2024