Numbers k such that k and k^2 use only the digits 0, 3, 4, 7 and 9.

Terms

a(0) =0a(1) =3a(2) =7a(3) =30a(4) =70a(5) =97a(6) =300a(7) =700a(8) =970a(9) =997a(10) =3000a(11) =7000a(12) =9700a(13) =9970a(14) =9997a(15) =30000a(16) =70000a(17) =97000a(18) =99700a(19) =99970a(20) =99997a(21) =300000a(22) =700000a(23) =970000a(24) =997000a(25) =999700a(26) =999970a(27) =999997a(28) =3000000a(29) =3074003