%I #17 May 11 2024 19:43:03
%S 2,3,11,15,28,46,63,65,104,105,143,188,1380,1599,3365,3549,4535,9192,
%T 11799,14745,45588,101657
%N Numbers k such that 3*10^k - 37 is prime.
%C For k > 1, numbers k such that the digit 2 followed by k-2 occurrences of the digit 9 followed by the digits 63 is prime (see Example section).
%C a(23) > 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 29w63</a>.
%e 2 is in this sequence because 3*10^2 - 37 = 263 is prime.
%e Initial terms and associated primes:
%e a(1) = 2, 263;
%e a(2) = 3, 2963;
%e a(3) = 11, 299999999963;
%e a(4) = 15, 2999999999999963;
%e a(5) = 28, 29999999999999999999999999963; etc.
%t Select[Range[2, 100000], PrimeQ[3*10^# - 37] &]
%o (PARI) isok(k) = isprime(3*10^k - 37); \\ _Michel Marcus_, Nov 15 2017
%Y Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
%K nonn,more,hard
%O 1,1
%A _Robert Price_, Nov 15 2017
%E a(22) from _Robert Price_, Jul 07 2018
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