

A056726


Numbers n such that 9*10^n + R_n is prime, where R_n = 11...1 is the repunit (A002275) of length n.


1



2, 5, 20, 41, 47, 92, 161, 401, 455, 8570, 18592, 73714, 78635, 100780
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OFFSET

1,1


COMMENTS

Also numbers n such that (82*10^n1)/9 is prime.


LINKS

Table of n, a(n) for n=1..14.
Makoto Kamada, Prime numbers of the form 911...11.
Index entries for primes involving repunits


MATHEMATICA

Do[ If[ PrimeQ[ 9*10^n + (10^n1)/9], Print[n]], {n, 0, 5000}]


CROSSREFS

Cf. A002275, A093634.
Sequence in context: A247131 A192164 A244087 * A176042 A185593 A136899
Adjacent sequences: A056723 A056724 A056725 * A056727 A056728 A056729


KEYWORD

hard,nonn


AUTHOR

Robert G. Wilson v, Aug 11 2000


EXTENSIONS

8570 from Hugo Pfoertner, Oct 22 2004
a(11)a(14) from Robert Price, Dec 05 2014


STATUS

approved



