Numbers k such that k and k^2 use only the digits 0, 1, 2, 7 and 9.

Terms

a(0) =0a(1) =1a(2) =10a(3) =11a(4) =27a(5) =100a(6) =101a(7) =110a(8) =270a(9) =1000a(10) =1001a(11) =1010a(12) =1011a(13) =1100a(14) =1101a(15) =1127a(16) =2700a(17) =2777a(18) =10000a(19) =10001a(20) =10010a(21) =10011a(22) =10100a(23) =10110a(24) =11000a(25) =11001a(26) =11010a(27) =11270a(28) =11277a(29) =27000