

A296059


Numbers k such that (10^k/8 + 1)/9 is prime.


0



4, 7, 16, 43, 58, 106, 160, 229, 628, 1579, 3805, 16153, 31420
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OFFSET

1,1


COMMENTS

Equivalently, numbers k such that (10^k + 8)/72 is prime.


LINKS



EXAMPLE

139, 138889, and 138888888888889 are prime, so 4, 7, and 16 are in the sequence.


MATHEMATICA

ParallelMap[ If[ PrimeQ[(10^#/8 +1)/9], #, Nothing] &, Range@ 10000] (* Robert G. Wilson v, Dec 08 2017 *)


PROG

(PARI) isok(k) = (k>2) && isprime((10^k/8 + 1)/9); \\ Michel Marcus, Dec 05 2017


CROSSREFS



KEYWORD

nonn,more


AUTHOR



EXTENSIONS



STATUS

approved



