Numbers k such that 7^k ends with k.

Terms

a(0) =3a(1) =43a(2) =343a(3) =2343a(4) =72343a(5) =172343a(6) =5172343a(7) =65172343a(8) =565172343a(9) =1565172343a(10) =11565172343a(11) =511565172343