Numbers k such that k and k^2 use only the digits 2, 3, 4, 7 and 8.

Terms

a(0) =2a(1) =22a(2) =28a(3) =88a(4) =278a(5) =472a(6) =478a(7) =482a(8) =2872a(9) =2878a(10) =4832a(11) =47732a(12) =47778a(13) =47838a(14) =48722a(15) =48872a(16) =272732a(17) =278832a(18) =287878a(19) =887878a(20) =2728338a(21) =2788778a(22) =4844878a(23) =8847838a(24) =27243878a(25) =27244878a(26) =27283472a(27) =27828732a(28) =28782438a(29) =47373872