

A293277


Numbers k such that (77*10^k  257)/9 is prime.


0



2, 3, 5, 8, 9, 23, 24, 32, 69, 96, 243, 381, 2237, 2426, 2427, 4041, 5195, 5516, 7053, 9690, 33933, 66237, 93249
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OFFSET

1,1


COMMENTS

For k > 1, numbers k such that the digit 8 followed by k2 occurrences of the digit 5 followed by the digits 27 is prime (see Example section).
a(24) > 2*10^5.


LINKS



EXAMPLE

3 is in this sequence because (77*10^3  257)/9 = 8527 is prime.
Initial terms and associated primes:
a(1) = 2, 827;
a(2) = 3, 8527;
a(3) = 5, 855527;
a(4) = 8, 855555527;
a(5) = 9, 8555555527; etc.


MATHEMATICA

Select[Range[1, 100000], PrimeQ[(77*10^#  257)/9] &]


CROSSREFS



KEYWORD

nonn,more,hard


AUTHOR



STATUS

approved



