

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
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OFFSET

1,1


COMMENTS

Primes of the form 10^n9 (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: 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



