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 A103075 Numbers n such that 8*10^n + 2*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
 1, 2, 4, 5, 8, 10, 22, 223, 254, 350, 379, 401, 436, 1154, 1246, 2053, 2687, 3725, 4271, 13096, 21427, 30266, 36791, 41759 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also numbers n such that (74*10^n+7)/9 is prime. a(25) > 10^5. - Robert Price, Oct 15 2015 LINKS Table of n, a(n) for n=1..24. Makoto Kamada, Prime numbers of the form 822...223. Index entries for primes involving repunits. FORMULA a(n) = A101062(n) + 1. MATHEMATICA Do[ If[ PrimeQ[(74*10^n + 7)/9], Print[n]], {n, 0, 10000}] PROG (PARI) for(n=0, 50000, if(isprime((74*10^n+7)/9), print1(n", "))) \\ Altug Alkan, Oct 15 2015 CROSSREFS Cf. A002275, A101062. Sequence in context: A018767 A018332 A018257 * A294940 A322125 A174803 Adjacent sequences: A103072 A103073 A103074 * A103076 A103077 A103078 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Jan 19 2005 EXTENSIONS a(20)-a(21) from Kamada data by Robert Price, Dec 14 2010 a(22)-a(24) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013 STATUS approved

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Last modified May 27 02:16 EDT 2024. Contains 372847 sequences. (Running on oeis4.)