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 A103078 Numbers n such that 8*10^n + 3*R_n + 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
 1, 2, 4, 9, 10, 15, 44, 55, 56, 124, 140, 279, 674, 848, 1420, 1462, 3314, 3442, 4141, 35625 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also numbers n such that (25*10^n+17)/3 is prime. a(21) > 10^5. - Robert Price, Oct 20 2015 LINKS Makoto Kamada, Prime numbers of the form 833...339. FORMULA a(n) = A101065(n) + 1. MATHEMATICA Do[ If[ PrimeQ[(25*10^n + 17)/3], Print[n]], {n, 0, 10000}] PROG (PARI) for(n=1, 1e3, if(isprime((25*10^n+17)/3), print1(n", "))) \\ Altug Alkan, Oct 20 2015 CROSSREFS Cf. A002275, A101065. Sequence in context: A287413 A026602 A287436 * A060756 A075347 A005733 Adjacent sequences:  A103075 A103076 A103077 * A103079 A103080 A103081 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Jan 19 2005 EXTENSIONS a(20) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013 STATUS approved

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Last modified May 27 12:27 EDT 2020. Contains 334657 sequences. (Running on oeis4.)