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A103092 Numbers n such that 9*10^n-7 is prime. 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

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.

LINKS

Table of n, a(n) for n=1..26.

Makoto Kamada, Factorizations of 899...993.

Index entries for primes involving repunits.

MATHEMATICA

Do[ If[ PrimeQ[9*10^n - 7], Print[n]], {n, 0, 10000}]

CROSSREFS

Sequence in context: A124257 A066385 A226913 * 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

STATUS

approved

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Last modified October 24 12:11 EDT 2014. Contains 248516 sequences.