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A159298
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Numbers k such that k * 10^k * (10^k - 1)/9 + 1 is prime.
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0
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OFFSET
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1,2
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COMMENTS
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There are no more terms up to k = 4000 (cf. link).
There are no more terms up to k = 14600. - Jason Earls, Nov 30 2009
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REFERENCES
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J. Earls, Mathematical Bliss, Pleroma Publications, 2009, page 55. ASIN: B002ACVZ6O [From Jason Earls, Nov 22 2009]
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LINKS
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EXAMPLE
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For k=5, k * 10^k * (10^k - 1)/9 + 1 is the prime 5555500001, so 5 is a term.
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PROG
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(Magma) [ x[1]: x in [ < n, Integers()!(n*10^n*(10^n - 1)/9 + 1) >: n in [1..186] ] | IsPrime(x[2]) ];
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CROSSREFS
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Cf. A002275 (repunits: (10^n - 1)/9).
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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a(8) from Herman Jamke (hermanjamke(AT)fastmail.fm), Oct 03 2010
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STATUS
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approved
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