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 A093177 Primes of the form 90*R_n + 1, where R_n is the repunit (A002275) of length n. 10
 991, 99991, 9999991, 999999999999999999999999999999991, 999999999999999999999999999999999999999999991, 999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999991 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primes of the form 10^n-9 (n=3,5,7,...). -  Vincenzo Librandi, Nov 16 2010 LINKS Makoto Kamada, Prime numbers of the form 99...991. FORMULA a(n) =  10^(A056696(n)+1) - 9 = 10^A095714(n) - 9. CROSSREFS Cf. A056696 (corresponding n), A095714. Sequence in context: A137703 A255098 A155509 * A161926 A172698 A109149 Adjacent sequences:  A093174 A093175 A093176 * A093178 A093179 A093180 KEYWORD nonn AUTHOR Rick L. Shepherd, Mar 27 2004 EXTENSIONS Edited by Ray Chandler, Feb 26 2012 STATUS approved

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Last modified March 22 06:01 EDT 2018. Contains 301047 sequences. (Running on oeis4.)