Numbers k such that k and k^2 use only the digits 0, 1, 4 and 6.

Terms

a(0) =0a(1) =1a(2) =4a(3) =10a(4) =40a(5) =100a(6) =400a(7) =1000a(8) =4000a(9) =10000a(10) =40000a(11) =100000a(12) =400000a(13) =1000000a(14) =4000000a(15) =10000000a(16) =40000000a(17) =100000000a(18) =400000000a(19) =1000000000a(20) =4000000000a(21) =10000000000a(22) =40000000000a(23) =100000000000a(24) =400000000000a(25) =1000000000000