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设{an}是公差不为0的等差数列,a1=2且a1,a3,a6成等比数列,则{an}的前n项...
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设{a
n}是公差不为0的等差数列,a
1=2且a
1,a
3,a
6成等比数列,则{a
n}的前n项和S
n=( )
A.
![](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACkAAAAqCAYAAAAu9HJYAAAAAXNSR0IArs4c6QAAAARnQU1BAACx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)
B.
![](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACkAAAAqCAYAAAAu9HJYAAAAAXNSR0IArs4c6QAAAARnQU1BAACx
jwv8YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAAIKSURBVFhH7ZiNrcMgDISZjJ1Yh2UyCqPwcPhP
ABuHJk31KlVV1UC+3J0NVNgXvMQLGO0vQBqrpbBCwFvZ7SHZh0oaraw2nmxTDlRqG77eiku322gr
H1KTDunMVl8P6ZRU0fsJs42WIdP8uJCV3DQnj079BTkmQYIailPam+KNOziFQgKgTDZvVpMtH7Uv
yLdvbf7h87UtMYaQe9sJk/lPmVrSRCx9+zqNjYUIgH7eWpB8B1TJGZjRtXsBlTJBS3N51So+uFez
o2SUPqwoLkegWrZ4FWZdRLHqE1SAbi0WQckwAQDCqPi5is+vWVZlopNqPathpId0UNK1mDgJZGi1
kluyFerEW51Vi7lsF+YO6YMdNxA5yJeE3JfRXHh1HMuOEaAHmxgHCZksqnaQjS70on7Ym18cpR9l
4zHII1TsjVOZ/LiSzOCdG33Z+NdukNc084aS9Up1XLno33MLYqqZhn2r3dVzfRqSY8tJ+E9DXnWa
Nb5s9ISN6prCmSItNxp+c4Nx3g9pTHUshlY2DzlpxZSIx4uJu62DkvNWcCHTYoDJmLZq8U4MK7iQ
+7jgGrYE9zNJtOIS5M7pjhXIsbcJOWPFVUjKKaCvJNGKa5D9w1c5L/KvGm7FNGQ46MWVjlA3yJ+o
N+USe9CBkjQrsBus+L2GZFixAgKb4/5lESNq/P4PyRCtOeQVSv4Bwg4pFPNhuxcAAAAASUVORK5C
YII=
)
C.
![](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACkAAAAqCAYAAAAu9HJYAAAAAXNSR0IArs4c6QAAAARnQU1BAACx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)
D.n
2+n
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