Numbers whose decimal expansion contains only 0's and 5's.

Terms

a(0) =0a(1) =5a(2) =50a(3) =55a(4) =500a(5) =505a(6) =550a(7) =555a(8) =5000a(9) =5005a(10) =5050a(11) =5055a(12) =5500a(13) =5505a(14) =5550a(15) =5555a(16) =50000a(17) =50005a(18) =50050a(19) =50055a(20) =50500a(21) =50505a(22) =50550a(23) =50555a(24) =55000a(25) =55005a(26) =55050a(27) =55055a(28) =55500a(29) =55505