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A272523 Numbers k such that (265*10^k + 17)/3 is prime.

%I A272523 #16 May 26 2024 16:02:36
%S A272523 2,3,4,10,35,60,65,72,87,218,226,326,365,461,611,1244,1566,4839,4913,
%T A272523 5396,7020,8410,9714,10362,11405,21695,25240,56076,56588,74579,81990,
%U A272523 114736
%N A272523 Numbers k such that (265*10^k + 17)/3 is prime.
%C A272523 For k > 1, numbers k such that the digits 88 followed by k-1 occurrences of the digit 3 followed by the digit 9 is prime (see Example section).
%C A272523 a(33) > 2*10^5.
%H A272523 Makoto Kamada, <a href="https://stdkmd.net/nrr">Factorization of near-repdigit-related numbers</a>.
%H A272523 Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/prime_difficulty.txt">Search for 883w9</a>.
%e A272523 3 is in this sequence because (265*10^3 + 17)/3 = 88339 is prime.
%e A272523 Initial terms and associated primes:
%e A272523 a(1) = 2, 8839;
%e A272523 a(2) = 3, 88339;
%e A272523 a(3) = 4, 883339;
%e A272523 a(4) = 10, 883333333339;
%e A272523 a(5) = 35, 8833333333333333333333333333333333339, etc.
%t A272523 Select[Range[0, 100000], PrimeQ[(265*10^# + 17)/3] &]
%o A272523 (PARI) is(n)=ispseudoprime((265*10^n + 17)/3) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y A272523 Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
%K A272523 nonn,more
%O A272523 1,1
%A A272523 _Robert Price_, May 01 2016
%E A272523 a(32) from _Robert Price_, Mar 21 2020