Numbers k such that k and k^2 use only the digits 0, 1, 6 and 7.

Terms

a(0) =0a(1) =1a(2) =10a(3) =100a(4) =1000a(5) =10000a(6) =100000a(7) =1000000a(8) =1077776a(9) =10000000a(10) =10777760a(11) =100000000a(12) =107777600a(13) =1000000000a(14) =1077776000a(15) =10000000000a(16) =10777760000a(17) =100000000000a(18) =107777600000a(19) =1000000000000