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

Terms

a(0) =1a(1) =3a(2) =11a(3) =27a(4) =111a(5) =139a(6) =173a(7) =177a(8) =373a(9) =1139a(10) =1339a(11) =1927a(12) =2777a(13) =3373a(14) =11123a(15) =13123a(16) =17123a(17) =17923a(18) =17927a(19) =19777a(20) =27927a(21) =117123a(22) =133123a(23) =173139a(24) =193373a(25) =199277a(26) =279177a(27) =312911a(28) =373139a(29) =1127927