Numbers k such that k and k^2 use only the digits 0, 1, 4, 7 and 9.

Terms

a(0) =0a(1) =1a(2) =7a(3) =10a(4) =70a(5) =97a(6) =100a(7) =107a(8) =700a(9) =701a(10) =970a(11) =997a(12) =1000a(13) =1007a(14) =1049a(15) =1070a(16) =1071a(17) =7000a(18) =7001a(19) =7010a(20) =7071a(21) =9700a(22) =9701a(23) =9970a(24) =9997a(25) =10000a(26) =10007a(27) =10070a(28) =10097a(29) =10490