问题
填空题
已知数列{an}中，an=
|
答案
an=
=(2n)2 (2n-1)(2n+1)
=1+4n2 4n2-1
=1+1 4n2-1
(1 2
-1 2n-1
)1 2n+1
∴Sn=n+
(1-1 2
+1 3
-1 3
+…+1 5
-1 2n-1
)1 2n+1
=n+
(1-1 2
)=n+1 2n+1
，n 2n+1
∴lim n→∞
=Sn n
(1+lim n→∞
)=11 2n+1
故答案为：1