Numbers k such that k and k^2 use only the digits 0, 4, 5, 6 and 7.

Terms

a(0) =0a(1) =74a(2) =76a(3) =740a(4) =760a(5) =7400a(6) =7600a(7) =74000a(8) =74476a(9) =76000a(10) =77766a(11) =667574a(12) =740000a(13) =744760a(14) =757666a(15) =760000a(16) =777660a(17) =777666a(18) =6675740a(19) =7075076a(20) =7400000a(21) =7447600a(22) =7576660a(23) =7600000a(24) =7776600a(25) =7776660a(26) =66757400a(27) =67577766a(28) =67607474a(29) =70750760