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%I #54 Jan 17 2019 13:44:08
%S 2,3,4,5,6,8,10,14,15,62,98,184,190,389,430,815,918,1124,1284,9544,
%T 10068,16514,24756,39880,86478,179138
%N Numbers k such that 3*10^k + 89 is prime.
%C For k>1, numbers such that the digit 3 followed by k-2 occurrences of the digit 0 followed by the digits 89 is prime (see Example section).
%C a(27) > 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 30w89.</a>
%e 3 is in this sequence because 3*10^3 + 89 = 3089 is prime.
%e Initial terms and primes associated:
%e a(1) = 2, 389;
%e a(2) = 3, 3089;
%e a(3) = 4, 30089;
%e a(4) = 5, 300089;
%e a(5) = 6, 3000089; etc.
%t Select[Range[0, 100000], PrimeQ[3*10^# + 89] &]
%o (PARI) isok(k) = ispseudoprime(3*10^k + 89); \\ _Altug Alkan_, Mar 30 2018
%Y Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
%K nonn,more,hard
%O 1,1
%A _Robert Price_, Mar 23 2017
%E a(26) from _Robert Price_, Oct 22 2018
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