

A257038


Numbers k such that 9*R_(k+2)  5*10^k is prime, where R_k = 11...1 is the repunit (A002275) of length k.


0




OFFSET

1,1


COMMENTS

Also, numbers k such that 95*10^k  1 is prime.
Terms from Kamada.
a(9) > 1170000.


LINKS



EXAMPLE

For k=3, 9*R_5  5*10^3 = 99999  5000 = 94999 which is prime.


MATHEMATICA

Select[Range[0, 1170000], PrimeQ[95*10^#1 ] &]


PROG



CROSSREFS



KEYWORD

more,hard,nonn


AUTHOR



STATUS

approved



