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 A103089 Numbers n such that 8*10^n + 7*R_n - 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
 0, 5, 6, 185, 401, 480, 1319, 5646, 6029, 16824, 62387, 70638 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also numbers n such that (79*10^n-61)/9 is prime. a(13) > 10^5. - Robert Price, Oct 25 2015 LINKS Makoto Kamada, Prime numbers of the form 877...771. FORMULA a(n) = A101076(n+1) + 1, for n>1. MATHEMATICA Do[ If[ PrimeQ[(79*10^n - 61)/9], Print[n]], {n, 0, 10000}] CROSSREFS Cf. A002275, A101076. Sequence in context: A266718 A041257 A041411 * A041601 A301648 A041827 Adjacent sequences:  A103086 A103087 A103088 * A103090 A103091 A103092 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Jan 19 2005 EXTENSIONS 1 more term. Next term exceeds 50000. Sean A. Irvine, Sep 10 2009 Inserted a(1)=0 and added a(11)-a(12) by Robert Price, Oct 25 2015 STATUS approved

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Last modified January 19 03:54 EST 2020. Contains 331031 sequences. (Running on oeis4.)