Numbers k such that 4*R_k + 3*10^k - 1 is prime, where R_k = 11...11 is the repunit (A002275) of length k.

A259130

Numbers k such that 4*R_k + 3*10^k - 1 is prime, where R_k = 11...11 is the repunit (A002275) of length k.

Terms

    a(0) =0a(1) =6a(2) =12a(3) =492a(4) =5568a(5) =24756

External references