%I #10 May 24 2021 01:02:50
%S 3,54,58,64,70,253,438,4255,8770
%N Numbers k such that A344423(k) is prime.
%C a(10) > 10000. - _Hugo Pfoertner_, May 19 2021
%e A344423(3) = 100111001 is prime, so 3 is a term of the sequence.
%o (PARI) is(n) = ispseudoprime(10^(2*n+2) + 111*10^n + 1)
%Y Cf. A070247, A100580, A344423.
%K nonn,hard,more
%O 1,1
%A _Felix Fröhlich_, May 18 2021
%E a(9) from _Hugo Pfoertner_, May 19 2021