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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 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. 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.)