-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)^n243-729+2187=1701这三个数分别是243,-729,2187
243-7292187
