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

Terms

a(0) =0a(1) =3a(2) =27a(3) =30a(4) =270a(5) =300a(6) =2700a(7) =3000a(8) =27000a(9) =30000a(10) =270000a(11) =300000a(12) =2700000a(13) =3000000a(14) =27000000a(15) =27032203a(16) =27077797a(17) =30000000a(18) =30332997a(19) =270000000a(20) =270322030a(21) =270777970a(22) =300000000a(23) =303329970a(24) =2700000000a(25) =2703220300a(26) =2707779700a(27) =2720293723a(28) =2779023223a(29) =3000000000