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 A103092 Numbers n such that 9*10^n-7 is prime. 1
 0, 1, 6, 9, 10, 12, 13, 23, 61, 194, 233, 549, 765, 973, 1061, 1186, 1853, 3713, 6789, 7254, 7765, 9025, 10855, 23640, 31440, 31839, 32287, 120342, 132148 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Also numbers n such that 8*10^n + 9*R_n - 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n. a(30) > 2*10^5. - Robert Price, Sep 04 2015 LINKS Makoto Kamada, Prime numbers of the form 899...993. FORMULA a(n) = A101079(n-1) + 1 for n>1. EXAMPLE For n=0, 9*10^n-7=2 which is prime, so 0 is in the sequence. MATHEMATICA Do[ If[ PrimeQ[9*10^n - 7], Print[n]], {n, 0, 10000}] PROG (MAGMA) [n: n in [0..300] | IsPrime(9*10^n-7)]; // Vincenzo Librandi, Sep 05 2015 (PARI) is(n)=ispseudoprime(9*10^n-7) \\ Charles R Greathouse IV, Jun 12 2017 CROSSREFS Cf. A002275, A101079. Sequence in context: A066385 A226913 A293826 * A104523 A091886 A111774 Adjacent sequences:  A103089 A103090 A103091 * A103093 A103094 A103095 KEYWORD more,nonn AUTHOR Robert G. Wilson v, Jan 19 2005 EXTENSIONS One more term from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008 a(23)-a(26) from Kamada data by Robert Price, Dec 14 2010 Inserted a(1)=0 by Robert Price, Sep 04 2015 a(28)-a(29) from Robert Price, Sep 04 2015 STATUS approved

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Last modified May 31 20:23 EDT 2020. Contains 334748 sequences. (Running on oeis4.)