Numbers k such that k and k^2 use only the digits 0, 2, 5, 7 and 8.

Terms

a(0) =0a(1) =5a(2) =50a(3) =85a(4) =500a(5) =505a(6) =755a(7) =850a(8) =2255a(9) =5000a(10) =5005a(11) =5050a(12) =5085a(13) =7550a(14) =7555a(15) =8500a(16) =8705a(17) =8805a(18) =22550a(19) =22555a(20) =50000a(21) =50005a(22) =50050a(23) =50085a(24) =50500a(25) =50505a(26) =50555a(27) =50850a(28) =72255a(29) =75500