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A032480 Numbers k such that 207*2^k + 1 is prime. 1
2, 3, 4, 6, 7, 10, 14, 15, 16, 34, 42, 44, 46, 62, 66, 106, 127, 130, 171, 202, 231, 232, 238, 248, 256, 296, 314, 412, 604, 956, 1023, 1287, 1454, 1564, 1766, 2036, 5215, 5911, 6092, 9190, 9916, 10410, 13456, 14336, 14444, 15490, 30835, 32558, 34770, 41218 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Jeppe Stig Nielsen, Table of n, a(n) for n = 1..68 (terms n = 1..66 from Robert Price)

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

Ray Ballinger, Proth Search Page

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

MATHEMATICA

f[n_]:=PrimeQ[207*2^n+1]; lst={}; Do[If[f[n], AppendTo[lst, n]], {n, 7!}]; lst (* Vladimir Joseph Stephan Orlovsky, Mar 03 2010 *)

Select[Range[1000], PrimeQ[207*2^# + 1] & ] (* Robert Price, Dec 19 2018 *)

PROG

(PARI) is(n)=ispseudoprime(207*2^n+1) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

Sequence in context: A035941 A039854 A237752 * A226137 A163771 A194855

Adjacent sequences:  A032477 A032478 A032479 * A032481 A032482 A032483

KEYWORD

nonn,hard

AUTHOR

N. J. A. Sloane

EXTENSIONS

a(50)-a(66) from the Ray Ballinger and Wilfrid Keller link by Robert Price, Dec 19 2018

STATUS

approved

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Last modified January 23 15:51 EST 2021. Contains 340385 sequences. (Running on oeis4.)