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%I #12 Jun 02 2024 14:05:46
%S 2,7,10,34,53,59,62,241,298,485,731,899,1231,4702,7010,8573,9205,9724,
%T 17045,24950,136384
%N Numbers k such that (62*10^k - 791)/9 is prime.
%C For k > 1, numbers k such that the digit 6 followed by k-2 occurrences of the digit 8 followed by the digits 01 is prime (see Example section).
%C a(22) > 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/prime_difficulty.txt">Search for 68w01</a>.
%e 2 is in this sequence because (62*10^2 - 791)/9 = 601 is prime.
%e Initial terms and associated primes:
%e a(1) = 2, 601;
%e a(2) = 7, 68888801;
%e a(3) = 10, 68888888801;
%e a(4) = 34, 68888888888888888888888888888888801;
%e a(5) = 53, 688888888888888888888888888888888888888888888888888801; etc.
%t Select[Range[1, 100000], PrimeQ[(62*10^# - 791)/9] &]
%Y Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
%K nonn,more,hard
%O 1,1
%A _Robert Price_, Sep 27 2017
%E a(21) from _Robert Price_, Jun 02 2019
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