用棋子摆方阵恰好摆成每边为20的实心方阵，若改为4层空心方阵，最外层每边应放几枚？(x-T2S;N+g*T/v9I7Q'S/x
算式：提示.T.C3]+i7C4a0K)W4T.U;x'I(x-T2S;N+g*T/v9I7Q'S/x
答：最外层每边应放8l4y)~.k'r9^-X(g-{枚。(x-T2S;N+g*T/v9I7Q'S/x