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%I #13 May 25 2024 17:54:24
%S 0,2,3,4,14,27,35,42,53,60,89,117,126,137,162,207,281,472,2752,3381,
%T 6462,12183,14910,29205,40883,50675,78717,83880,99113
%N Numbers k such that 8*10^k + 39 is prime.
%C For k > 1, numbers k such that the digit 8 followed by k-2 occurrences of the digit 0 followed by the digits 39 is prime (see Example section).
%C a(30) > 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 80w39</a>.
%e 3 is in this sequence because 8*10^3 + 39 = 8039 is prime.
%e Initial terms and associated primes:
%e a(1) = 0, 47;
%e a(2) = 2, 839;
%e a(3) = 3, 8039;
%e a(4) = 4, 80039;
%e a(5) = 14, 800000000000039; etc.
%t Select[Range[0, 100000], PrimeQ[8*10^# + 39] &]
%Y Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
%K nonn,more,hard
%O 1,2
%A _Robert Price_, Jan 10 2017