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A032478 Numbers k such that 203*2^k + 1 is prime. 0
13, 25, 29, 33, 45, 57, 65, 153, 197, 245, 637, 1785, 1917, 2045, 4925, 5313, 7449, 8437, 23645, 28273, 34217, 40189, 135125, 141477, 169077, 215945, 234229, 265089, 482177, 556069, 1335989, 1357425, 1966689, 2526505 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..34.

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[0, 1000], PrimeQ[203*2^# + 1] &] (* Robert Price, Dec 09 2018 *)

PROG

(PARI) is(n)=ispseudoprime(203*2^n+1) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

Sequence in context: A335374 A335466 A186403 * A280925 A161603 A075033

Adjacent sequences:  A032475 A032476 A032477 * A032479 A032480 A032481

KEYWORD

nonn,hard

AUTHOR

N. J. A. Sloane

EXTENSIONS

a(25)-a(32) from Ray Ballinger and Wilfrid Keller link by Robert Price, Dec 09 2018

a(33) from updated Ray Ballinger and Wilfrid Keller link by Robert Price, Dec 10 2018

a(34) from Jeppe Stig Nielsen, Apr 04 2020

STATUS

approved

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Last modified August 8 11:12 EDT 2020. Contains 336293 sequences. (Running on oeis4.)