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 A102950 Numbers k such that 2*10^k + R_k + 8 is prime, where R_k = 11...1 is the repunit (A002275) of length k. 1
 1, 223, 318, 427, 3727, 5227, 8779, 11383, 15415, 26382 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also numbers k such that (19*10^k + 71)/9 is prime. a(11) > 10^5. - Robert Price, Feb 06 2015 LINKS Table of n, a(n) for n=1..10. Makoto Kamada, Prime numbers of the form 211...119. Index entries for primes involving repunits. FORMULA a(n) = A101955(n) + 1. MATHEMATICA Do[ If[ PrimeQ[(19*10^n + 71)/9], Print[n]], {n, 0, 10000}] CROSSREFS Cf. A002275, A101955. Sequence in context: A271799 A152824 A142386 * A143801 A118818 A142437 Adjacent sequences: A102947 A102948 A102949 * A102951 A102952 A102953 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Dec 17 2004 EXTENSIONS Addition of a(8)-a(10) from Kamada data by Robert Price, Dec 13 2010 STATUS approved

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Last modified August 2 22:39 EDT 2024. Contains 374875 sequences. (Running on oeis4.)