

A056717


Numbers n such that 6*10^n + R_n is prime, where R_n = 11...1 is the repunit (A002275) of length n.


1



1, 5, 7, 25, 31, 112, 199, 533, 616, 718, 787, 1357, 2779, 3889, 4192, 7537, 7945, 23938, 32632, 49169, 56453, 61097, 90211
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OFFSET

1,2


COMMENTS

Also numbers n such that (55*10^n1)/9 is prime.


LINKS

Table of n, a(n) for n=1..23.
Makoto Kamada, Prime numbers of the form 611...11.
Index entries for primes involving repunits


MATHEMATICA

Do[ If[ PrimeQ[ 6*10^n + (10^n1)/9], Print[n]], {n, 0, 10000}]


CROSSREFS

Cf. A002275, A093631.
Sequence in context: A298900 A166660 A037374 * A072370 A057490 A057253
Adjacent sequences: A056714 A056715 A056716 * A056718 A056719 A056720


KEYWORD

nonn


AUTHOR

Robert G. Wilson v, Aug 11 2000


EXTENSIONS

2779,3889,4192,7537,7945 from Hugo Pfoertner, Oct 19 2004
23938 from Ray Chandler, Sep 25 2010
32632 and 49169 from Ray Chandler, Feb 08 2012
56453 from Serge Batalov, Mar 12 2009 confirmed as next term by Ray Chandler, Feb 09 2012
61097 from Ray Chandler, Feb 09 2012
90211 from Ray Chandler, Feb 10 2012


STATUS

approved



