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

A331860

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) =6a(1) =7a(2) =12a(3) =31a(4) =58a(5) =127a(6) =454a(7) =556a(8) =558a(9) =604a(10) =2944a(11) =8118a(12) =12078a(13) =16942a(14) =26268a(15) =45198

External references