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 A103022 Numbers n such that 5*10^n + 8*R_n - 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
 3, 5, 6, 21, 309, 816, 858, 1115, 1419, 1689, 12009, 18693, 28098, 90965 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Also numbers n such that (53*10^n-71)/9 is prime. a(15) > 10^5. - Robert Price, Sep 08 2015 LINKS Makoto Kamada, Prime numbers of the form 588...881. FORMULA a(n) = A101587(n) + 1. MATHEMATICA Do[ If[ PrimeQ[(53*10^n - 71)/9], Print[n]], {n, 0, 10000}] CROSSREFS Cf. A002275, A101587. Sequence in context: A295403 A272440 A276704 * A086189 A137082 A242501 Adjacent sequences:  A103019 A103020 A103021 * A103023 A103024 A103025 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Jan 18 2005 EXTENSIONS Addition of a(11)-a(13) from Kamada data by Robert Price, Dec 13 2010 a(14) from Robert Price, Sep 08 2015 STATUS approved

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Last modified August 10 06:08 EDT 2022. Contains 356029 sequences. (Running on oeis4.)