Primes of the form 5*10^k + 7*R_k, where R_k is the repunit (A002275) of length k.

A093941

Primes of the form 5*10^k + 7*R_k, where R_k is the repunit (A002275) of length k.

Terms

    a(0) =5a(1) =577a(2) =577777777

External references