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A050553 Numbers n such that 55*2^n-1 is prime. 0
1, 3, 5, 7, 15, 33, 41, 57, 69, 75, 77, 131, 133, 153, 247, 305, 351, 409, 471, 1251, 1259, 2253, 2411, 2425, 2699, 3221, 4099, 4173, 4291, 4905, 5349, 6723, 7143, 7505, 10539, 10557, 12099, 17373, 23721, 27895, 33801, 35519, 45927, 63589, 73287, 96933, 106659, 218043, 253047, 397941, 651015 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..51.

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

Kosmaj, Riesel list k<300.

PROG

(PARI) is(n)=ispseudoprime(55*2^n-1) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

Cf. A057813.

Sequence in context: A261646 A303027 A217615 * A005540 A155802 A080741

Adjacent sequences:  A050550 A050551 A050552 * A050554 A050555 A050556

KEYWORD

hard,nonn

AUTHOR

N. J. A. Sloane, Dec 29 1999

EXTENSIONS

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

STATUS

approved

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Last modified October 18 20:21 EDT 2019. Contains 328197 sequences. (Running on oeis4.)