5*n analog to Keith numbers.

Terms

a(0) =2a(1) =4a(2) =6a(3) =8a(4) =9a(5) =10a(6) =12a(7) =14a(8) =16a(9) =18a(10) =19a(11) =28a(12) =56a(13) =147a(14) =566a(15) =1301a(16) =4288a(17) =8576a(18) =13088a(19) =119396a(20) =518800a(21) =634825a(22) =654780a(23) =993476a(24) =2109420a(25) =3034105a(26) =6466772a(27) =17838948a(28) =80148824