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 A093947 Primes of the form 8*10^n - 1. 0
 7, 79, 79999, 799999, 799999999, 79999999999, 79999999999999999999999999, 79999999999999999999999999999999999999999999999999, 79999999999999999999999999999999999999999999999999999999999999999999999999999 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Equivalently, primes of the form 7*10^n + 9*R_n, where R_n is the repunit (A002275) of length n. LINKS Makoto Kamada, Prime numbers of the form 799...99. MATHEMATICA Select[Table[FromDigits[PadRight[{7}, n, 9]], {n, 50}], PrimeQ] (* Vincenzo Librandi, May 08 2019 *) PROG (MAGMA) [a: n in [0..200] | IsPrime(a) where a is (8*10^n-1)]; // Vincenzo Librandi, May 08 2019 CROSSREFS Cf. A056721 (corresponding n). Sequence in context: A201704 A331424 A052385 * A222137 A115986 A295843 Adjacent sequences:  A093944 A093945 A093946 * A093948 A093949 A093950 KEYWORD nonn AUTHOR Rick L. Shepherd, Apr 17 2004 STATUS approved

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Last modified February 28 06:55 EST 2020. Contains 332321 sequences. (Running on oeis4.)