-1,3,-9,27,-81,243,-729,2187,
-1*(-3)^0,-1*(-3)^1,-1*(-3)^2,-1*(-3)^3,-1*(-3)^4,-1*(-3)^5,-1*(-3)^6.,-1*(-3)^n
243-729+2187=1701
这三个数分别是243,-729,2187