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 A103016 Numbers n such that 5*10^n + 4*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
 1, 3, 4, 6, 10, 21, 30, 72, 199, 208, 270, 396, 619, 759, 1077, 1383, 1566, 1960, 2653, 3504, 3786, 6085, 13110, 36448, 39582, 47989, 50998, 66729 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also numbers n such that (49*10^n+41)/9 is prime. a(29) > 10^5. - Robert Price, Jul 21 2015 LINKS Makoto Kamada, Prime numbers of the form 544...449. EXAMPLE a(n) = A101581(n) + 1. MATHEMATICA Do[ If[ PrimeQ[(49*10^n + 41)/9], Print[n]], {n, 0, 10000}] CROSSREFS Cf. A002275, A101581. Sequence in context: A052548 A232268 A103049 * A061032 A091424 A092839 Adjacent sequences:  A103013 A103014 A103015 * A103017 A103018 A103019 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Jan 18 2005 EXTENSIONS Addition of a(23) from Kamada data by Robert Price, Dec 09 2010 a(24)-a(26) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013 a(27)-a(28) from Robert Price, Jul 21 2015 STATUS approved

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Last modified August 17 11:34 EDT 2017. Contains 290635 sequences.