Numbers k such that k and k^2 use only the digits 0, 4, 6, 7 and 9.

Terms

a(0) =0a(1) =7a(2) =64a(3) =70a(4) =97a(5) =640a(6) =700a(7) =970a(8) =997a(9) =6400a(10) =6907a(11) =7000a(12) =7064a(13) =9700a(14) =9970a(15) =9997a(16) =64000a(17) =69070a(18) =70000a(19) =70640a(20) =77974a(21) =97000a(22) =99700a(23) =99747a(24) =99970a(25) =99997a(26) =640000a(27) =666907a(28) =667907a(29) =690700