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A108327
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Integers n such that 10^n-21 is a prime number.
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3
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2, 6, 32, 108, 408, 1286, 2268, 2328, 4284, 53558, 181182, 249010
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listen;
history;
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internal format)
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OFFSET
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1,1
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COMMENTS
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a(13) > 2.5*10^5. - Robert Price, Apr 12 2015
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LINKS
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Table of n, a(n) for n=1..12.
Makoto Kamada, Near-repdigit numbers of the form AA...AABA.
Makoto Kamada, Prime numbers of the form 99...9979.
Index entries for primes involving repunits.
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EXAMPLE
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6 is a member because 10^6-21 = 1000000-21 = 999979, which is prime.
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CROSSREFS
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Cf. A089675, A095714, A092767.
Sequence in context: A109243 A223586 A212762 * A188573 A196010 A121071
Adjacent sequences: A108324 A108325 A108326 * A108328 A108329 A108330
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KEYWORD
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more,nonn
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AUTHOR
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Julien Peter Benney (jpbenney(AT)ftml.net), Jun 30 2005
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EXTENSIONS
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Edited by Ray Chandler, Dec 23 2010
a(10)=53558 from Robert Price, Mar 03 2011
a(11)-a(12) from Kamada data by Robert Price, Apr 12 2015
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STATUS
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approved
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