Squares composed of digits {1,2,4}.

Terms

a(0) =1a(1) =4a(2) =121a(3) =144a(4) =441a(5) =1444a(6) =114244a(7) =2214144a(8) =11142244a(9) =121242121a(10) =421111441a(11) =1111422244a(12) =44424414441a(13) =111114222244