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A093177 Primes of the form 90*R_n + 1, where R_n is the repunit (A002275) of length n. 9
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,..,) [From Vincenzo Librandi, Nov 16 2010]

LINKS

Table of n, a(n) for n=1..6.

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: A031790 A137703 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 November 21 14:12 EST 2014. Contains 249779 sequences.