Numbers k such that k and k^2 use only the digits 1, 3, 4, 7 and 9.

Terms

a(0) =1a(1) =3a(2) =7a(3) =19479a(4) =134143a(5) =379143a(6) =439479a(7) =971479a(8) =1199143a(9) =37917979a(10) =97339479a(11) =199434143a(12) =314917979a(13) =413934143a(14) =443979479a(15) =974379143a(16) =1191399143a(17) =1979379143a(18) =3799934143a(19) =4439979479a(20) =13943149479a(21) =34317917979a(22) =199949471479