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A111391 Numbers n such that 11*10^n - 1 is prime. 1
1, 9, 11, 17, 22, 29, 36, 37, 52, 166, 448, 2011, 3489, 4871, 6982, 10024, 16974, 33287, 47364, 58873, 126160 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Numbers n such that 10^(n+1) + (10^n-1) is a prime.

LINKS

Table of n, a(n) for n=1..21.

Gary Barnes, Primes of the form k*10^n-1

MATHEMATICA

Do[ If[ PrimeQ[10^(n + 1) + (10^n - 1)], Print[n]], {n, 9500}]

CROSSREFS

Cf. A096209.

Sequence in context: A075824 A228951 A108113 * A077788 A137018 A182391

Adjacent sequences:  A111388 A111389 A111390 * A111392 A111393 A111394

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Nov 15 2005

EXTENSIONS

a(16)-a(19) from Ray Chandler, Sep 16 2013

a(20)-a(21) from P. Kurtovic submitted by Ray Chandler, Sep 17 2013

STATUS

approved

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Last modified April 17 07:07 EDT 2014. Contains 240634 sequences.