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 A001775 Numbers n such that 19*2^n-1 is prime. (Formerly M2506 N0991) 5
 1, 3, 5, 21, 41, 49, 89, 133, 141, 165, 189, 293, 305, 395, 651, 665, 771, 801, 923, 953, 3689, 5315, 6989, 15641, 48819, 78389, 134053, 167843, 181395, 311091, 353661, 645555, 916763 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES H. Riesel, ``Prime numbers and computer methods for factorization,'' Progress in Mathematics, Vol. 57, Birkhauser, Boston, 1985, Chap. 4, see pp. 381-384. N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence). N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). H. C. Williams and C. R. Zarnke, Math. Comp., 22 (1968), 420-422. LINKS Kosmaj, Riesel list k<300. Wilfrid Keller, List of primes k.2^n - 1 for k < 300 PROG (PARI) is(n)=ispseudoprime(19*2^n-1) \\ Charles R Greathouse IV, Feb 17 2017 CROSSREFS Cf. A032359, 19*2^n+1 is prime. Sequence in context: A288152 A082699 A096729 * A148548 A148549 A148550 Adjacent sequences:  A001772 A001773 A001774 * A001776 A001777 A001778 KEYWORD hard,nonn AUTHOR EXTENSIONS More terms from Hugo Pfoertner, Jun 22 2004 More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008 Minor corrections by Charles R Greathouse IV, Aug 29 2010 STATUS approved

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Last modified December 15 20:00 EST 2019. Contains 330000 sequences. (Running on oeis4.)