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 A103091 Numbers n such that 8*10^n + 7*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 2
 1, 3, 6, 31, 36, 61, 117, 229, 339, 3165, 3958, 5277, 5343, 6079, 6535, 8485, 15084, 34537 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also numbers n such that (79*10^n+11)/9 is prime. a(19) > 10^5. - Robert Price, Oct 27 2015 LINKS Makoto Kamada, Prime numbers of the form 877...779. FORMULA a(n) = A101078(n) + 1. MATHEMATICA Do[ If[ PrimeQ[(79*10^n + 11)/9], Print[n]], {n, 0, 10000}] CROSSREFS Cf. A002275, A101078. Sequence in context: A117805 A154135 A182274 * A186940 A101751 A274999 Adjacent sequences: A103088 A103089 A103090 * A103092 A103093 A103094 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Jan 19 2005 EXTENSIONS a(17) from Kamada data by Robert Price, Dec 14 2010 a(18) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013 STATUS approved

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Last modified March 28 21:15 EDT 2023. Contains 361596 sequences. (Running on oeis4.)