Numbers k such that k and k^2 use only the digits 2, 4, 5, 7 and 9.

Terms

a(0) =2a(1) =5a(2) =7a(3) =27a(4) =77a(5) =477a(6) =527a(7) =977a(8) =2227a(9) =5477a(10) =7227a(11) =7277a(12) =22977a(13) =49727a(14) =49777a(15) =54277a(16) =97977a(17) =99727a(18) =99777a(19) =229727a(20) =274727a(21) =495477a(22) =499227a(23) =499277a(24) =724727a(25) =774227a(26) =2792477a(27) =4945477a(28) =4952227a(29) =4957277