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试题详情及答案解析
数列{a
n
}的前n项和为S
n
,且满足a
n
+2
=a
n
+1
-a
n
(n∈N
*
),a
1
=1,a
2
=2,则S
2014
=_________.
答案
:3;
试题分析:∵a
n
+1
=a
n
-a
n
-1
(n≥2),a
1
=1,a
2
=2,
∴a
3
=1,a
4
=-1,a
5
=-2,a
6
=-1,a
7
=1,a
8
=2,
即数列{a
n
}是以6为周期的周期数列,且6项的和为0,
∵2014=6×335+4
∴S
2014
=a
1
+a
2
+a
3
+a
4
=3
故答案为:3
考点:递推数列,数列的通项与前n项和
2015届四川省成都市新都区高三诊断测试理科数学试卷(带解析)