

A103055


Numbers n such that 7*10^n + 3*R_n  2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.


1



1, 3, 4, 5, 6, 9, 12, 31, 59, 69, 74, 287, 489, 592, 634, 1089, 1607, 3141, 5962, 6267, 9678, 11431, 12927, 32189, 38700, 53033, 83525
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OFFSET

1,2


COMMENTS

Also numbers n such that (22*10^n7)/3 is prime.


LINKS

Table of n, a(n) for n=1..27.
Makoto Kamada, Prime numbers of the form 733...331.
Index entries for primes involving repunits.


FORMULA

a(n) = A101137(n) + 1.


MATHEMATICA

Do[ If[ PrimeQ[(22*10^n  7)/3], Print[n]], {n, 0, 10000}]


CROSSREFS

Cf. A002275, A101137.
Sequence in context: A088875 A022884 A105857 * A128995 A293306 A014101
Adjacent sequences: A103052 A103053 A103054 * A103056 A103057 A103058


KEYWORD

more,nonn


AUTHOR

Robert G. Wilson v, Jan 19 2005


EXTENSIONS

a(22)a(23) Kamada link by Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(24)a(25) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013
a(26)a(27) from Erik Branger Sep 08 2014 by Ray Chandler, Apr 23 2015


STATUS

approved



