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A108329 Integers n such that 10^n-27 is prime. 3
2, 4, 7, 14, 20, 22, 29, 31, 40, 80, 85, 224, 767, 952, 3592, 4016, 4187, 9239, 17684, 20716, 30791 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

See Kamada link - primecount.txt for terms, primesize.txt for discovery details including probable or proved primes - search on "99973".

The next term, if one exists, is >100000. [From Robert Price, Apr 25 2011]

LINKS

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

Makoto Kamada, List of near-repdigit-related prime numbers.

Index entries for primes involving repunits.

EXAMPLE

n = 7 is a member because: 10^7-27 = 10000000-27 = 9999973, which is prime.

CROSSREFS

Cf. A089675, A095714, A092767, A176987.

Sequence in context: A133638 A018505 A280430 * A057264 A045514 A102957

Adjacent sequences:  A108326 A108327 A108328 * A108330 A108331 A108332

KEYWORD

more,nonn

AUTHOR

Julien Peter Benney (jpbenney(AT)ftml.net), Jun 30 2005

EXTENSIONS

a(18)-a(19) from Kamada data by Robert Price, Dec 10 2010

a(20)-a(21) from Robert Price, Dec 15 2010

Edited by Ray Chandler, Dec 23 2010

STATUS

approved

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Last modified September 26 05:09 EDT 2017. Contains 292502 sequences.