

A103016


Numbers n such that 5*10^n + 4*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.


1



1, 3, 4, 6, 10, 21, 30, 72, 199, 208, 270, 396, 619, 759, 1077, 1383, 1566, 1960, 2653, 3504, 3786, 6085, 13110, 36448, 39582, 47989, 50998, 66729
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OFFSET

1,2


COMMENTS

Also numbers n such that (49*10^n+41)/9 is prime.
a(29) > 10^5.  Robert Price, Jul 21 2015


LINKS

Table of n, a(n) for n=1..28.
Makoto Kamada, Prime numbers of the form 544...449.
Index entries for primes involving repunits.


EXAMPLE

a(n) = A101581(n) + 1.


MATHEMATICA

Do[ If[ PrimeQ[(49*10^n + 41)/9], Print[n]], {n, 0, 10000}]


CROSSREFS

Cf. A002275, A101581.
Sequence in context: A052548 A232268 A103049 * A061032 A091424 A092839
Adjacent sequences: A103013 A103014 A103015 * A103017 A103018 A103019


KEYWORD

more,nonn


AUTHOR

Robert G. Wilson v, Jan 18 2005


EXTENSIONS

Addition of a(23) from Kamada data by Robert Price, Dec 09 2010
a(24)a(26) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013
a(27)a(28) from Robert Price, Jul 21 2015


STATUS

approved



