Numbers k such that R(k) - 10^floor(k/2-1) is prime, where R(k) = (10^k-1)/9 (repunit: A002275).

A331863

Numbers k such that R(k) - 10^floor(k/2-1) is prime, where R(k) = (10^k-1)/9 (repunit: A002275).

Terms

    a(0) =8a(1) =12a(2) =17a(3) =20a(4) =24a(5) =42a(6) =1124a(7) =1169a(8) =1538a(9) =7902a(10) =27617a(11) =29684

External references