Numbers which have only digits 4 and 5 in base 10.

Terms

a(0) =4a(1) =5a(2) =44a(3) =45a(4) =54a(5) =55a(6) =444a(7) =445a(8) =454a(9) =455a(10) =544a(11) =545a(12) =554a(13) =555a(14) =4444a(15) =4445a(16) =4454a(17) =4455a(18) =4544a(19) =4545a(20) =4554a(21) =4555a(22) =5444a(23) =5445a(24) =5454a(25) =5455a(26) =5544a(27) =5545a(28) =5554a(29) =5555