Numbers k such that k and k^2 use only the digits 2, 4, 7, 8 and 9.

Terms

a(0) =2a(1) =7a(2) =22a(3) =27a(4) =28a(5) =88a(6) =222a(7) =278a(8) =288a(9) =472a(10) =478a(11) =882a(12) =972a(13) =2788a(14) =2878a(15) =4722a(16) =4778a(17) =4788a(18) =8788a(19) =8882a(20) =28772a(21) =28788a(22) =49272a(23) =49277a(24) =49472a(25) =49722a(26) =49777a(27) =49778a(28) =49788a(29) =49827