Primes of the form 9*10^k + 7*R_k, where R_k is the repunit (A002275) of length k.

A093944

Primes of the form 9*10^k + 7*R_k, where R_k is the repunit (A002275) of length k.

Terms

    a(0) =97a(1) =977a(2) =97777

External references