Repdigital lucky numbers.

Terms

a(0) =1a(1) =3a(2) =7a(3) =9a(4) =33a(5) =99a(6) =111a(7) =777a(8) =9999a(9) =33333a(10) =55555a(11) =111111a(12) =777777a(13) =7777777a(14) =55555555