%I

%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 FrÃ¶hlich_, May 18 2021

%E a(9) from _Hugo Pfoertner_, May 19 2021