Numbers with digits 4 and 6 only.

Terms

a(0) =4a(1) =6a(2) =44a(3) =46a(4) =64a(5) =66a(6) =444a(7) =446a(8) =464a(9) =466a(10) =644a(11) =646a(12) =664a(13) =666a(14) =4444a(15) =4446a(16) =4464a(17) =4466a(18) =4644a(19) =4646a(20) =4664a(21) =4666a(22) =6444a(23) =6446a(24) =6464a(25) =6466a(26) =6644a(27) =6646a(28) =6664a(29) =6666