Absolute lucky numbers: every permutation of digits is a lucky number.

Terms

a(0) =1a(1) =3a(2) =7a(3) =9a(4) =13a(5) =15a(6) =31a(7) =33a(8) =37a(9) =51a(10) =73a(11) =99a(12) =111a(13) =115a(14) =151a(15) =339a(16) =393a(17) =511a(18) =777a(19) =933a(20) =9999a(21) =33333a(22) =55555a(23) =111111a(24) =777777a(25) =7777777a(26) =55555555