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A032353 Numbers k such that 7*2^k+1 is prime. 6
2, 4, 6, 14, 20, 26, 50, 52, 92, 120, 174, 180, 190, 290, 320, 390, 432, 616, 830, 1804, 2256, 6614, 13496, 15494, 16696, 22386, 54486, 88066, 95330, 207084, 283034, 561816, 804534, 811230, 1491852, 2139912, 2167800, 2915954, 3015762, 3511774, 5775996 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..41.

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

Eric Weisstein's World of Mathematics, Proth Prime

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

MATHEMATICA

Select[Range[10^3], PrimeQ[7*2^# + 1] &] (* Michael De Vlieger, Feb 25 2017 *)

PROG

(PARI) is(n)=ispseudoprime(7*2^n+1) \\ Charles R Greathouse IV, Feb 20 2017

(MAGMA) [n: n in [1..830] | IsPrime(7*2^n+1)]; // Arkadiusz Wesolowski, Feb 24 2017

CROSSREFS

Cf. A002255, A050527.

Sequence in context: A277909 A064409 A225078 * A062112 A226302 A284886

Adjacent sequences:  A032350 A032351 A032352 * A032354 A032355 A032356

KEYWORD

nonn,hard

AUTHOR

James R. Buddenhagen

EXTENSIONS

Added more terms (from http://web.archive.org/web/20161028080239/http://www.prothsearch.net/riesel.html), Joerg Arndt, Apr 07 2013

a(41) from Jeppe Stig Nielsen, Jul 25 2019

STATUS

approved

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Last modified December 8 01:42 EST 2019. Contains 329850 sequences. (Running on oeis4.)