A050842 - OEIS

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A050842

Numbers k such that 181*2^k-1 is prime.

0

3, 5, 7, 9, 11, 17, 23, 31, 35, 43, 47, 83, 85, 99, 101, 195, 267, 281, 363, 391, 519, 623, 653, 673, 701, 1091, 1147, 1565, 3273, 3661, 3923, 4127, 4783, 5267, 5345, 5747, 6151, 6299, 7569, 9033, 11843, 14139, 14175, 15779, 21557, 32295, 49823, 60979, 65195, 132367, 133895, 186827, 212647

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..53.

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

Kosmaj, Riesel list k<300.

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

MATHEMATICA

Select[Range[1000], PrimeQ[181*2^# - 1] & ] (* Robert Price, Dec 29 2018 *)

PROG

(PARI) is(n)=ispseudoprime(181*2^n-1) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

Sequence in context: A322553 A302601 A064076 * A143447 A318777 A152484

Adjacent sequences: A050839 A050840 A050841 * A050843 A050844 A050845

KEYWORD

hard,nonn

AUTHOR

N. J. A. Sloane, Dec 29 1999

EXTENSIONS

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008

a(49)-a(53) from the Wilfrid Keller link by Robert Price, Dec 29 2018

STATUS

approved