Primes of the form 3*10^k + 7*R_k, where R_k is the repunit (A002275) of length k.

A093939

Primes of the form 3*10^k + 7*R_k, where R_k is the repunit (A002275) of length k.

Terms

    a(0) =3a(1) =37a(2) =377777777777

External references