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

Terms

a(0) =2a(1) =3a(2) =7a(3) =27a(4) =223a(5) =473a(6) =4943a(7) =49777a(8) =222327a(9) =273393a(10) =477277a(11) =499423a(12) =499473a(13) =973393a(14) =2733943a(15) =4932923a(16) =4993443a(17) =4994777a(18) =4997927a(19) =49342927a(20) =49924277a(21) =49972927a(22) =49993443a(23) =49994223a(24) =49994777a(25) =97339223a(26) =492942927a(27) =494342927a(28) =497332327a(29) =497794473