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 A103010 Numbers k such that 5*10^k + 2*R_k + 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k. 1
 3, 5, 33, 48, 59, 60, 74, 126, 177, 228, 638, 1304, 1644, 2435, 4374, 8750, 15114, 16853, 30353, 30545, 36236 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Also numbers k such that (47*10^k + 43)/9 is prime. a(22) > 10^5. - Robert Price, Jul 10 2015 LINKS Table of n, a(n) for n=1..21. Makoto Kamada, Prime numbers of the form 522...227. Index entries for primes involving repunits. FORMULA a(n) = A101575(n) + 1. MATHEMATICA Do[ If[ PrimeQ[(46*10^n + 43)/9], Print[n]], {n, 0, 10000}] CROSSREFS Cf. A002275, A101575. Sequence in context: A235267 A284379 A372718 * A225866 A332704 A263295 Adjacent sequences: A103007 A103008 A103009 * A103011 A103012 A103013 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Jan 18 2005 EXTENSIONS a(17)-a(18) from Kamada data by Robert Price, Dec 14 2010 a(19)-a(21) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013 STATUS approved

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Last modified August 2 19:53 EDT 2024. Contains 374875 sequences. (Running on oeis4.)