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 A102945 Numbers n such that 10^n + 8*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 3
 1, 3, 12, 267, 843, 6300, 37992, 54117, 121242, 121621 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also numbers n such that (17*10^n+1)/9 is prime. No more terms below 133000. [Serge Batalov, May 15 2010] a(11) > 2*10^5. - Robert Price, Nov 16 2014 LINKS Makoto Kamada, Prime numbers of the form 188...889. FORMULA a(n) = A102031(n) + 1. MAPLE A102945:=n->`if`(isprime((17*10^n+1)/9), n, NULL): seq(A102945(n), n=1..10^3); # Wesley Ivan Hurt, Nov 16 2014 MATHEMATICA Do[ If[ PrimeQ[(17*10^n + 1)/9], Print[n]], {n, 0, 10000}] Select[Range[1000], PrimeQ[(17 10^# + 1) / 9] &] (* Vincenzo Librandi, Nov 17 2014 *) PROG (MAGMA) [n: n in [0..300] | IsPrime((17*10^n+1) div 9)]; // Vincenzo Librandi, Nov 17 2014 CROSSREFS Cf. A002275, A102031. Sequence in context: A321603 A297564 A280086 * A300532 A249940 A132515 Adjacent sequences:  A102942 A102943 A102944 * A102946 A102947 A102948 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Dec 16 2004 EXTENSIONS More PRP terms a(7)-a(10). Sieved with srsieve and tested with Prime95 by Serge Batalov, May 15 2010 STATUS approved

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Last modified April 1 14:52 EDT 2020. Contains 333163 sequences. (Running on oeis4.)