

A103010


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


1



3, 5, 33, 48, 59, 60, 74, 126, 177, 228, 638, 1304, 1644, 2435, 4374, 8750, 15114, 16853, 30353, 30545, 36236
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OFFSET

1,1


COMMENTS

Also numbers k such that (47*10^k + 43)/9 is prime.


LINKS



FORMULA



MATHEMATICA

Do[ If[ PrimeQ[(46*10^n + 43)/9], Print[n]], {n, 0, 10000}]


CROSSREFS



KEYWORD

more,nonn


AUTHOR



EXTENSIONS

a(19)a(21) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013


STATUS

approved



