{1},宽缓渗{2,3,4},{5,6,7,8,9},{10,11,12,13,14,15,16},…前n组共有1+3+5+…+(2n-1)=n2个正整数,故 An=(1+2+3+…+n2)-[1+2+3+…慎脊+(n-1)2](哪肆用前n组的和减去前n-1组的和) = n2(1+n2) 2 - (n?1)2[1+(n?1)2] 2 =(2n-1)(n2-n+1)Bn=n3-(n-1)3故An+Bn=2n3故答案为:2n3