| 1 |
| 2 |
| 1 |
| 4 |
| 1 |
| 8 |
| 1 |
| 16 |
Sn＝(1+
| 1 |
| 2 |
| 1 |
| 4 |
| 1 |
| 8 |
| 1 |
| 16 |
| 1 |
| 2 n |
=（1+2+3+4+…+n）+（
| 1 |
| 2 |
| 1 |
| 4 |
| 1 |
| 8 |
| 1 |
| 2 n |
=
| n(n+1) |
| 2 |
| ||||
1?
|
=
| n2+n+2 |
| 2 |
| 1 |
| 2 n |
故答案为：
| n2+n+2 |
| 2 |
| 1 |
| 2 n |
数列112，214，318，4116，…，的前n项之和等于______
数列1
，2
，3
，4
，…，的前n项之和
Sn＝(1+
) +(2+
)+(3+
)+(4+
)+…+(n+
)
=（1+2+3+4+…+n）+（
+
+
+…+
）
=
+
=
?
．
故答案为：
?
．
Sn＝(1+
=（1+2+3+4+…+n）+（
=
=
故答案为：
