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 A103108 Numbers n such that 9*10^n + 8*R_n - 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
 2, 3, 32, 42, 75, 368, 1392, 16350, 49101, 49689, 91839 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Also numbers n such that (89*10^n-53)/9 is prime. a(12) > 10^5. - Robert Price, Nov 12 2015 LINKS Table of n, a(n) for n=1..11. Makoto Kamada, Prime numbers of the form 988...883. Index entries for primes involving repunits. FORMULA a(n) = A101017(n) + 1. MATHEMATICA Do[ If[ PrimeQ[(89*10^n - 53)/9], Print[n]], {n, 0, 10000}] CROSSREFS Cf. A002275, A101017. Sequence in context: A176894 A041053 A212763 * A107124 A141049 A354612 Adjacent sequences: A103105 A103106 A103107 * A103109 A103110 A103111 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Jan 19 2005 EXTENSIONS a(8) from Kamada data by Robert Price, Dec 14 2010 a(9)-a(10) from Erik Branger May 01 2013 by Ray Chandler, Aug 17 2013 a(11) from Robert Price, Nov 12 2015 STATUS approved

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Last modified March 5 03:04 EST 2024. Contains 370537 sequences. (Running on oeis4.)