Squares that remain squares prefixed with a 2.

Terms

a(0) =25a(1) =2500a(2) =7225a(3) =75625a(4) =250000a(5) =722500a(6) =2325625a(7) =7562500a(8) =25000000a(9) =72250000a(10) =232562500a(11) =268140625a(12) =756250000a(13) =2500000000a(14) =7225000000a(15) =23256250000a(16) =26814062500a(17) =68971890625a(18) =75625000000a(19) =250000000000a(20) =722500000000