

A108327


Integers n such that 10^n21 is a prime number.


3



2, 6, 32, 108, 408, 1286, 2268, 2328, 4284, 53558, 181182, 249010
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OFFSET

1,1


COMMENTS

a(13) > 2.5*10^5.  Robert Price, Apr 12 2015


LINKS

Table of n, a(n) for n=1..12.
Makoto Kamada, Nearrepdigit numbers of the form AA...AABA.
Makoto Kamada, Prime numbers of the form 99...9979.
Index entries for primes involving repunits.


EXAMPLE

6 is a member because 10^621 = 100000021 = 999979, which is prime.


CROSSREFS

Cf. A089675, A095714, A092767.
Sequence in context: A109243 A223586 A212762 * A188573 A196010 A121071
Adjacent sequences: A108324 A108325 A108326 * A108328 A108329 A108330


KEYWORD

more,nonn


AUTHOR

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


EXTENSIONS

Edited by Ray Chandler, Dec 23 2010
a(10)=53558 from Robert Price, Mar 03 2011
a(11)a(12) from Kamada data by Robert Price, Apr 12 2015


STATUS

approved



