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A103100
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Numbers n such that 9*10^n + 5*R_n - 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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0, 3, 6, 18, 30, 88, 93, 154, 177, 228, 573, 897, 981, 1416, 1450, 3366, 4932, 5194, 13479, 18609, 23346, 51424, 74676, 80571
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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 (86*10^n-41)/9 is prime.
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LINKS
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FORMULA
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EXAMPLE
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For n=0, (86*10^n - 41)/9 = 5 which is prime.
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MATHEMATICA
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Do[ If[ PrimeQ[(86*10^n - 41)/9], Print[n]], {n, 0, 10000}]
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PROG
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(PARI) for(n=0, 1e3, if(ispseudoprime((86*10^n-41)/9), print1(n, ", "))) \\ Altug Alkan, Nov 10 2015
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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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Inserted a(1)=0 and added a(22)-a(24) by Robert Price, Nov 10 2015
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STATUS
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approved
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