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%I #11 Mar 18 2020 16:26:43
%S 2,3,4,5,9,27,35,44,88,104,205,290,302,381,400,686,917,1150,2278,2757,
%T 3220,3316,7469,9535,21442,46409,103718,123688,147139
%N Numbers k such that (148*10^k - 1)/3 is prime.
%C Numbers k such that the digits 49 followed by k occurrences of the digit 3 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/primedifficulty.txt">Search for 493w</a>.
%e 3 is in this sequence because (148*10^3-1)/3 = 233329 is prime.
%e Initial terms and primes associated:
%e a(1) = 2, 4933;
%e a(2) = 3, 49333;
%e a(3) = 4, 493333;
%e a(4) = 5, 4933333;
%e a(5) = 9, 49333333333, etc.
%t Select[Range[0, 100000], PrimeQ[(148*10^# - 1)/3] &]
%o (PARI) is(n)=ispseudoprime((148*10^n - 1)/3) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
%K nonn,more
%O 1,1
%A _Robert Price_, Jun 18 2016
%E a(27)-a(29) from _Robert Price_, Mar 18 2020
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