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A002234
Numbers k such that the Woodall number k*2^k - 1 is prime.
(Formerly M0820 N0311)
29
2, 3, 6, 30, 75, 81, 115, 123, 249, 362, 384, 462, 512, 751, 822, 5312, 7755, 9531, 12379, 15822, 18885, 22971, 23005, 98726, 143018, 151023, 667071, 1195203, 1268979, 1467763, 2013992, 2367906, 3752948, 17016602
OFFSET
1,1
COMMENTS
a(34) = 17016602 is tentative until the range 16838832..17016601 is fully searched. - Eric W. Weisstein, Mar 22 2018
REFERENCES
J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 115, p. 40, Ellipses, Paris 2008.
R. K. Guy, Unsolved Problems in Number Theory, Springer, 1st edition, 1981. See section B20.
F. Le Lionnais, Les Nombres Remarquables, Paris, Hermann, 1983, p. 95, 1983.
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).
David Wells, The Penguin Dictionary of Curious and Interesting Numbers. Penguin Books, NY, 1986, Revised edition 1987. See p. 139.
LINKS
Ray Ballinger and Wilfrid Keller, Woodall numbers.
C. K. Caldwell, Woodall Numbers.
Brady Haran and Matt Parker, 383 is cool, Numberphile video (2017).
Matt Parker and Brady Haran, 383 and Woodall Primes, Numberphile video (2017).
H. Riesel, Lucasian criteria for the primality of N=h.2^n-1, Math. Comp., 23 (1969), 869-875.
Eric Weisstein's World of Mathematics, Woodall Number.
Eric Weisstein's World of Mathematics, Integer Sequence Primes.
PROG
(PARI) is(n)=isprime(n<<n - 1) \\ Charles R Greathouse IV, Feb 07 2017
CROSSREFS
Cf. A050918 (for the actual primes), A003261, A005849.
Sequence in context: A330030 A192441 A108326 * A074005 A145499 A221310
KEYWORD
nonn,nice,hard
EXTENSIONS
a(27) communicated by Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Mar 15 2004
a(28) = 1195203 found by M. Rodenkirch; contributed by Eric W. Weisstein, Nov 29 2005
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008
a(30)-a(33) from John Blazek, May 14 2009
a(34) = 17016602 communicated by Eric W. Weisstein, Mar 22 2018
STATUS
approved