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A103015
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Numbers n such that 5*10^n + 4*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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2, 6, 8, 18, 53, 68, 242, 276, 320, 564, 620, 1782, 2340, 2454, 5765, 15530, 15605, 22938
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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 (49*10^n+23)/9 is prime.
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LINKS
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FORMULA
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MATHEMATICA
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Do[ If[ PrimeQ[(49*10^n + 23)/9], Print[n]], {n, 0, 10000}]
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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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STATUS
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approved
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