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 A103104 Numbers n such that 9*10^n + 6*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
 1, 2, 4, 7, 13, 28, 58, 86, 92, 108, 1408, 1486, 1712, 2674, 3880, 5536, 7588, 7650, 10558, 15532, 17959, 37180, 93082 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also numbers n such that (29*10^n+1)/3 is prime. a(24) > 10^5. - Robert Price, Nov 12 2015 LINKS Makoto Kamada, Prime numbers of the form 966...667. FORMULA a(n) = A101013(n) + 1. MATHEMATICA Do[ If[ PrimeQ[(29*10^n + 1)/3], Print[n]], {n, 0, 10000}] CROSSREFS Cf. A002275, A101013. Sequence in context: A265580 A136408 A317718 * A103480 A024826 A291481 Adjacent sequences:  A103101 A103102 A103103 * A103105 A103106 A103107 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Jan 19 2005 EXTENSIONS a(19)-a(21) from Kamada data by Robert Price, Dec 14 2010 a(22) from Erik Branger May 01 2013 by Ray Chandler, Aug 17 2013 a(23) from Robert Price, Nov 12 2015 STATUS approved

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Last modified August 7 22:11 EDT 2022. Contains 355995 sequences. (Running on oeis4.)