(x^2-2x+3)^7
= x^14 - 14x^13 + 105x^12 - 532x^11 + 2009x^10 - 5922x^9 + 13993x^8 - 26840x^7
　+ 41979x^6 - 53298x^5 + 54243x^4 - 43092x^3 + 25515x^2 - 10206x + 2187