

A103022


Numbers n such that 5*10^n + 8*R_n  7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.


1



3, 5, 6, 21, 309, 816, 858, 1115, 1419, 1689, 12009, 18693, 28098, 90965
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OFFSET

1,1


COMMENTS

Also numbers n such that (53*10^n71)/9 is prime.


LINKS



FORMULA



MATHEMATICA

Do[ If[ PrimeQ[(53*10^n  71)/9], Print[n]], {n, 0, 10000}]


CROSSREFS



KEYWORD

more,nonn


AUTHOR



EXTENSIONS

Addition of a(11)a(13) from Kamada data by Robert Price, Dec 13 2010


STATUS

approved



