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%I #8 Sep 16 2019 21:40:34
%S 1,2,4,7,10,11,29,35,52,56,106,217,580,673,808,1354,1666,3292,3770,
%T 8989,16525,24773,39301,125330,158407
%N Numbers k such that (77*10^k - 293)/9 is prime.
%C For k>1, numbers such that the digit 8 followed by k-2 occurrences of the digit 5 followed by the digits 23 is prime (see Example section).
%C a(26) > 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 85w23</a>.
%e 4 is in this sequence because (77*10^4 - 293)/9 = 85523 is prime.
%e Initial terms and primes associated:
%e a(1) = 1, 53;
%e a(2) = 2, 823;
%e a(3) = 4, 85523;
%e a(4) = 7, 85555523;
%e a(5) = 10, 85555555523; etc.
%t Select[Range[1, 100000], PrimeQ[(77*10^# - 293)/9] &]
%Y Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
%K nonn,more,hard
%O 1,2
%A _Robert Price_, Jun 09 2017
%E a(24)-a(25) from _Robert Price_, Sep 16 2019
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