Primes of the form 4*10^k + 7*R_k, where R_k is the repunit (A002275) of length k.

A093940

Primes of the form 4*10^k + 7*R_k, where R_k is the repunit (A002275) of length k.

Terms

    a(0) =47a(1) =47777

External references