Primes of the form 6*10^k + 7*R_k, where R_k is the repunit (A002275) of length k.

A093942

Primes of the form 6*10^k + 7*R_k, where R_k is the repunit (A002275) of length k.

Terms

    a(0) =67a(1) =677a(2) =67777a(3) =67777777777

External references