

A102937


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


3



0, 1, 2, 5, 7, 19, 20, 28, 58, 250, 397, 7591, 32716, 70978, 83587, 140693
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OFFSET

1,3


COMMENTS

Also numbers k such that (14*10^k + 13)/9 is prime.


LINKS



FORMULA



MATHEMATICA

Do[ If[ PrimeQ[(14*10^n + 13)/9], Print[n]], {n, 0, 10000}]


CROSSREFS



KEYWORD

more,nonn


AUTHOR



EXTENSIONS

a(13) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013


STATUS

approved



