Squares that remain squares when prefixed with a 7.

Terms

a(0) =225a(1) =5625a(2) =22500a(3) =562500a(4) =2250000a(5) =6125625a(6) =19580625a(7) =56250000a(8) =225000000a(9) =612562500a(10) =1958062500a(11) =2562890625a(12) =5625000000a(13) =22500000000a(14) =51472265625a(15) =61256250000a(16) =195806250000a(17) =256289062500a(18) =562500000000