问题 填空题
数列{an}满足an=
n(n+1)
2
(n∈N*),则
1
a1
+
1
a2
+…+
1
a2013
等于______.
答案

∵an=

n(n+1)
2
(n∈N*),

1
an
=2×(
1
n
-
1
n+1
),

1
a1
+
1
a2
+…+
1
a2013

=2[(1-

1
2
)+(
1
2
-
1
3
)+…+(
1
2013
-
1
2014
)]

=2(1-

1
2014

=

2013
1007

故答案为:

2013
1007

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