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 A002236 Numbers n such that 9*2^n - 1 is prime. (Formerly M2634 N1045) 7
 1, 3, 7, 13, 15, 21, 43, 63, 99, 109, 159, 211, 309, 343, 415, 469, 781, 871, 939, 1551, 3115, 3349, 5589, 5815, 5893, 7939, 8007, 11547, 12495, 22555, 23647, 35647, 83415, 103059, 184999, 275859, 384243, 484975, 503893, 828709, 1010277 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES H. Riesel, Lucasian criteria for the primality of N=h.2^n-1, Math. Comp., 23 (1969), 869-875. 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). LINKS Wilfrid Keller, List of primes k.2^n - 1 for k < 300 C. K. Caldwell, The Prime Pages Kosmaj, Riesel list k<300. MATHEMATICA b=9; i=0; Table[While[i++; cp=b*2^i-1; !PrimeQ[cp]]; i, {j, 1, 22}] (* Lei Zhou, Nov 08 2013 *) PROG (PARI) is(n)=ispseudoprime(9*2^n-1) \\ Charles R Greathouse IV, Feb 17 2017 CROSSREFS Cf. A050524. Sequence in context: A092734 A209839 A192854 * A255682 A080565 A164344 Adjacent sequences:  A002233 A002234 A002235 * A002237 A002238 A002239 KEYWORD hard,nonn,nice AUTHOR EXTENSIONS More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008 STATUS approved

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Last modified September 17 08:31 EDT 2019. Contains 327127 sequences. (Running on oeis4.)