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%I #8 Oct 14 2019 16:48:58
%S 1,2,3,8,11,13,17,28,46,67,136,536,619,746,2420,2672,8228,10861,13424,
%T 16047,18075,37720,56371,75055
%N Numbers k such that (26*10^k - 173)/3 is prime.
%C For k>1, numbers such that the digit 8 followed by k-2 occurrences of the digit 6 followed by the digits 09 is prime (see Example section).
%C a(25) > 2*10^5.
%H Makoto Kamada, <a href="https://stdkmd.net/nrr">Factorization of near-repdigit-related numbers</a>.
%H Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/primedifficulty.txt">Search for 86w09</a>.
%e 2 is in this sequence because (26*10^2 - 173)/3 = 809 is prime.
%e Initial terms and primes associated:
%e a(1) = 1, 29;
%e a(2) = 2, 809;
%e a(3) = 3, 8609;
%e a(4) = 8, 866666609;
%e a(5) = 11, 866666666609; etc.
%t Select[Range[1, 100000], PrimeQ[(26*10^# - 173)/3] &]
%Y Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
%K nonn,more,hard
%O 1,2
%A _Robert Price_, Oct 19 2017
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