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A103031
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Numbers n such that 6*10^n + 2*R_n + 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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OFFSET
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1,1
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COMMENTS
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Also numbers n such that (56*10^n+61)/9 is prime.
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LINKS
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Table of n, a(n) for n=1..3.
Makoto Kamada, Factorizations of 622...229.
Index entries for primes involving repunits.
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MATHEMATICA
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Do[ If[ PrimeQ[(56*10^n + 61)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
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Sequence in context: A036279 A156769 A029758 * A012474 A193119 A122579
Adjacent sequences: A103028 A103029 A103030 * A103032 A103033 A103034
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KEYWORD
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bref,more,nonn
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AUTHOR
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Robert G. Wilson v, Jan 18 2005
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STATUS
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approved
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