问题
填空题
数列{an}的通项公式为an=
|
答案
an=
=1 (n+1)(n+2)
-1 n+1
∴Sn=(1 n+2
-1 2
)+(1 3
-1 3
)+(1 4
-1 4
)+…+（1 5
-1 n+1
）=1 n+2
-1 2
=1 n+2
．n 2(n+2)
故答案为n 2(n+2)
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数列{an}的通项公式为an=
|
an=
=1 (n+1)(n+2)
-1 n+1
∴Sn=(1 n+2
-1 2
)+(1 3
-1 3
)+(1 4
-1 4
)+…+（1 5
-1 n+1
）=1 n+2
-1 2
=1 n+2
．n 2(n+2)
故答案为n 2(n+2)