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 A103042 Numbers n such that 6*10^n + 7*R_n - 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
 0, 2, 156, 1055, 1997, 8930, 9563, 19560, 26838, 63857 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also numbers n such that (61*10^n-43)/9 is prime. a(11) > 10^5. - Robert Price, Sep 12 2015 LINKS Makoto Kamada, Prime numbers of the form 677...773. FORMULA a(n) = A101535(n-1) + 1 for n>1. MATHEMATICA Do[ If[ PrimeQ[(61*10^n - 43)/9], Print[n]], {n, 0, 10000}] CROSSREFS Cf. A002275, A101535. Sequence in context: A332585 A000725 A151614 * A284458 A260886 A142006 Adjacent sequences:  A103039 A103040 A103041 * A103043 A103044 A103045 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Jan 18 2005 EXTENSIONS a(8)-a(9) from Kamada data by Robert Price, Dec 14 2010 Inserted a(1)=0 by Robert Price, Sep 12 2015 a(10) from Robert Price, Sep 12 2015 STATUS approved

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Last modified June 6 08:44 EDT 2020. Contains 334859 sequences. (Running on oeis4.)