

A102930


Numbers k such that 10^k + 2*R_k + 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.


2



1, 2, 4, 14, 25, 32, 56, 62, 811, 812, 1084, 2533, 11924, 49552
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OFFSET

1,2


COMMENTS

Also numbers k such that (11*10^k + 43)/9 is prime.
a(15) > 10^5.  Robert Price, Jan 16 2015


LINKS

Table of n, a(n) for n=1..14.
Makoto Kamada, Prime numbers of the form 122...227.
Index entries for primes involving repunits.


FORMULA

a(n) = A102010(n) + 1.


MATHEMATICA

Do[ If[ PrimeQ[(11*10^n + 43)/9], Print[n]], {n, 0, 10000}]


CROSSREFS

Cf. A002275, A102010.
Sequence in context: A350050 A096012 A261562 * A357996 A135113 A050564
Adjacent sequences: A102927 A102928 A102929 * A102931 A102932 A102933


KEYWORD

more,nonn


AUTHOR

Robert G. Wilson v, Dec 16 2004


EXTENSIONS

Addition of a(13) from Kamada data by Robert Price, Dec 12 2010
a(14) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013


STATUS

approved



