%I #24 Sep 08 2022 08:46:10
%S 4,11,17,23,26,79,82,221,526,821,1204,5392,13139,35879,60991,77669
%N Numbers k such that 10^k + 123456789 is prime.
%C a(14) > 20000.
%C a(17) > 2*10^5. - _Robert Price_, Oct 26 2019
%t Select[Range[10^4], PrimeQ[10^# + 123456789] &] (* _Robert Price_, Sep 08 2019 *)
%o (PARI) for(n=1,10^4,if(ispseudoprime(10^n + 123456789),print1(n,", ")))
%o (Magma) [n: n in [1..500] | IsPrime(10^n + 123456789)]; // _Vincenzo Librandi_, Oct 12 2014
%Y Cf. A248350, A248351, A248352, A050289.
%K nonn,more,hard
%O 1,1
%A _Derek Orr_, Oct 05 2014
%E a(14)-a(16) from _Robert Price_, Oct 26 2019