Numbers k such that k and k^2 use only the digits 0, 4, 5, 7 and 9.

Terms

a(0) =0a(1) =7a(2) =70a(3) =97a(4) =700a(5) =970a(6) =997a(7) =7000a(8) =9700a(9) =9747a(10) =9970a(11) =9997a(12) =70000a(13) =70997a(14) =75997a(15) =97000a(16) =97470a(17) =99700a(18) =99970a(19) =99997a(20) =700000a(21) =709970a(22) =709997a(23) =759970a(24) =759997a(25) =970000a(26) =974700a(27) =997000a(28) =999700a(29) =999970