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A102946
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Numbers n such that 2*10^n - 7 is prime.
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2
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1, 2, 3, 4, 6, 16, 21, 28, 48, 82, 122, 130, 282, 304, 4602, 12984, 13614, 42762, 90597, 109928, 158242
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OFFSET
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1,2
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COMMENTS
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Also numbers n such that 10^n + 9*R_n - 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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LINKS
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FORMULA
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MAPLE
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select(n -> isprime(2*10^n-7), [$0..10^4]); # Robert Israel, Nov 16 2014
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MATHEMATICA
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Do[ If[ PrimeQ[2*10^n - 7], Print[n]], {n, 0, 10000}]
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PROG
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CROSSREFS
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KEYWORD
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more,nonn
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AUTHOR
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EXTENSIONS
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More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
Addition of a(18)-a(19) from Kamada data by Robert Price, Dec 10 2010
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STATUS
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approved
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