Numbers k such that k and k^2 use only the digits 0, 1, 3 and 9.

Terms

a(0) =0a(1) =1a(2) =3a(3) =10a(4) =30a(5) =100a(6) =300a(7) =1000a(8) =3000a(9) =10000a(10) =30000a(11) =100000a(12) =300000a(13) =1000000a(14) =3000000a(15) =10000000a(16) =30000000a(17) =100000000a(18) =300000000a(19) =1000000000a(20) =3000000000a(21) =10000000000a(22) =30000000000a(23) =100000000000a(24) =300000000000a(25) =1000000000000