%I #19 Sep 08 2022 08:46:12
%S 3,192,1133,4763,5812,48467,130620,466002
%N 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.
%C Also, numbers k such that 95*10^k - 1 is prime.
%C Terms from Kamada.
%C a(9) > 1170000.
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/abaaa.htm">Near-repdigit numbers of the form ABAA...AA</a>.
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/9/94999.htm#prime">Prime numbers of the form 9499...99</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%e For k=3, 9*R_5 - 5*10^3 = 99999 - 5000 = 94999 which is prime.
%t Select[Range[0, 1170000], PrimeQ[95*10^#-1 ] &]
%o (Magma) [n: n in [0..400] | IsPrime(95*10^n-1)]; // _Vincenzo Librandi_, Apr 15 2015
%Y Cf. A002275.
%K more,hard,nonn
%O 1,1
%A _Robert Price_, Apr 14 2015
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