Squares composed of digits {0,2,4}.

Terms

a(0) =0a(1) =4a(2) =400a(3) =40000a(4) =2244004a(5) =4000000a(6) =42224004a(7) =224400400a(8) =400000000a(9) =424442404a(10) =4222400400a(11) =22200404004a(12) =22440040000a(13) =40000000000a(14) =42444240400a(15) =422240040000