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 A102994 Numbers n such that 4*10^n + 6*R_n - 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 3
 1, 2, 7, 9, 14, 24, 45, 49, 73, 74, 232, 338, 397, 504, 1063, 2817, 5305, 16768, 27060 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also numbers n such that (14*10^n-17)/3 is prime. a(20) > 10^5. - Robert Price, May 27 2015 LINKS Table of n, a(n) for n=1..19. Makoto Kamada, Prime numbers of the form 466...661. Index entries for primes involving repunits. FORMULA a(n) = A101729(n) + 1. MATHEMATICA Do[ If[ PrimeQ[(14*10^n - 17)/3], Print[n]], {n, 0, 10000}] CROSSREFS Cf. A002275, A101729. Sequence in context: A074244 A190565 A341631 * A226824 A168132 A211280 Adjacent sequences: A102991 A102992 A102993 * A102995 A102996 A102997 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Jan 17 2005 EXTENSIONS Addition of a(18)-a(19) from Kamada data by Robert Price, Dec 10 2010 STATUS approved

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Last modified July 17 22:08 EDT 2024. Contains 374377 sequences. (Running on oeis4.)