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A275523 Numbers k such that 2*10^k + 93 is prime.

%I A275523 #17 May 26 2024 15:49:40
%S A275523 1,2,6,7,8,11,42,73,115,131,163,178,247,320,343,346,736,1230,1556,
%T A275523 3746,5946,6020,6566,6770,11302,14024,29062,33268,37424,42187,49216,
%U A275523 51000,79242,81287
%N A275523 Numbers k such that 2*10^k + 93 is prime.
%C A275523 For k > 1, numbers k such that the digit 2 followed by k-2 occurrences of the digit 0 followed by the digits 93 is prime (see Example section).
%C A275523 a(35) > 10^5.
%H A275523 Makoto Kamada, <a href="https://stdkmd.net/nrr">Factorization of near-repdigit-related numbers</a>.
%H A275523 Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/prime_difficulty.txt">Search for 20w93</a>.
%e A275523 6 is in this sequence because 2*10^6 + 93 = 2000093 is prime.
%e A275523 Initial terms and associated primes:
%e A275523 a(1) = 1, 113;
%e A275523 a(2) = 2, 293;
%e A275523 a(3) = 6, 2000093;
%e A275523 a(4) = 7, 20000093;
%e A275523 a(5) = 8, 200000093, etc.
%t A275523 Select[Range[0, 100000], PrimeQ[2*10^# + 93] &]
%o A275523 (PARI) is(n)=ispseudoprime(2*10^n+93) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y A275523 Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
%K A275523 nonn,more
%O A275523 1,2
%A A275523 _Robert Price_, Jul 31 2016