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%I #9 Jan 17 2019 13:44:09
%S 2,3,6,14,17,29,41,44,87,213,354,840,972,1263,2018,2534,4868,7992,
%T 13676,18354,19304,40515,126638,135279
%N Numbers k such that (13*10^k + 437)/9 is prime.
%C For k>1, numbers such that the digit 1 followed by k-2 occurrences of the digit 4 followed by the digits 93 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 14w93.</a>
%e 3 is in this sequence because (13*10^3 + 437)/9 = 1493 is prime.
%e Initial terms and primes associated:
%e a(1) = 2, 193;
%e a(2) = 3, 1493;
%e a(3) = 6, 1444493;
%e a(4) = 14, 144444444444493;
%e a(5) = 17, 144444444444444493; etc.
%t Select[Range[0, 100000], PrimeQ[(13*10^# + 437)/9] &]
%Y Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
%K nonn,more,hard
%O 1,1
%A _Robert Price_, Feb 12 2017
%E a(23)-a(24) from _Robert Price_, Apr 14 2018
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