数列-1,4,-7,10,…,(-1)n(3n-2)的前n项和为Sn,则S11+ 发布时间:2017-05-03 16:38 │ 来源:www.tikuol.com 题型:选择题 问题: 数列-1,4,-7,10,…,(-1)n(3n-2)的前n项和为Sn,则S11+S20=( )A.-16B.30C.28D.14