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 A102939 Numbers n such that 10^n + 6*R_n - 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 2
 1, 2, 3, 18, 177, 324, 388, 392, 404, 531, 1083, 12546, 22443, 54388, 72916 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also numbers n such that (5*10^n-11)/3 is prime. a(16) > 10^5. - Robert Price, Nov 15 2014 LINKS Makoto Kamada, Prime numbers of the form 166...663. FORMULA a(n) = A102023(n) + 1. MAPLE A102939:=n->`if`(isprime((5*10^n-11)/3), n, NULL): seq(A102939(n), n=1..1000); # Wesley Ivan Hurt, Nov 15 2014 MATHEMATICA Do[ If[ PrimeQ[(5*10^n - 11)/3], Print[n]], {n, 0, 10000}] CROSSREFS Cf. A002275, A102023. Sequence in context: A076016 A226961 A107095 * A073983 A230602 A269343 Adjacent sequences:  A102936 A102937 A102938 * A102940 A102941 A102942 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Dec 16 2004 EXTENSIONS Addition of a(12)-a(13) from Kamada data by Robert Price, Dec 12 2010 a(14)-a(15) from Kamada data by Robert Price, Nov 15 2014 STATUS approved

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Last modified May 24 04:25 EDT 2019. Contains 323528 sequences. (Running on oeis4.)