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A003307
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Numbers k such that 2*3^k - 1 is prime.
(Formerly M0823)
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31
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1, 2, 3, 7, 8, 12, 20, 23, 27, 35, 56, 62, 68, 131, 222, 384, 387, 579, 644, 1772, 3751, 5270, 6335, 8544, 9204, 12312, 18806, 21114, 49340, 75551, 90012, 128295, 143552, 147488, 1010743, 1063844, 1360104
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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REFERENCES
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R. K. Guy, Unsolved Problems in Theory of Numbers, Section A3.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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PROG
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CROSSREFS
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Cf. A079363 (primes of the form 2*3^k - 1), A003306 (k such that 2*3^k + 1 is prime).
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KEYWORD
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nonn,hard,nice
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AUTHOR
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EXTENSIONS
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More terms from Douglas Burke (dburke(AT)nevada.edu)
Corrected and extended by Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008
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STATUS
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approved
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