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A057187
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Numbers n such that (21^n+1)/22 is a prime.
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14
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3, 5, 7, 13, 37, 347, 17597, 59183, 80761, 210599, 394579
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OFFSET
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1,1
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COMMENTS
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Some of the larger terms correspond to probable primes.
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LINKS
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Table of n, a(n) for n=1..11.
H. Dubner and T. Granlund, Primes of the Form (b^n+1)/(b+1), J. Integer Sequences, 3 (2000), #P00.2.7.
H. Lifchitz, Mersenne and Fermat primes field
Paul Bourdelais,A Generalized Repunit Conjecture [From Paul Bourdelais, Mar 24 2010]
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PROG
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(Prime95) PRP=1, 21, 394579, 1, 0, 0, "22"
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CROSSREFS
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Sequence in context: A047933 A075557 A244452 * A163080 A141414 A236464
Adjacent sequences: A057184 A057185 A057186 * A057188 A057189 A057190
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane, Sep 15 2000
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EXTENSIONS
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a(7) from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008
a(8) corresponds to a probable prime discovered by Paul Bourdelais, Mar 22 2010
a(9) corresponds to a probable prime discovered by Paul Bourdelais, Mar 24 2010
a(10) corresponds to a probable prime discovered by Paul Bourdelais, Aug 30 2013
a(11) corresponds to a probable prime discovered by Paul Bourdelais, Oct 23 2018
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STATUS
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approved
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