试题:
数列{an}中,a1=1,an=
1
an-1
+1
,则a4等于(  )
A.
5
3
B.
4
3
C.1D.
2
3

答案:

我来补答
由题意得,a2=
1
a1
+1=
1
1
+1
=2,a3=
1
a2
+1
=
1
2
+1=
3
2
a4=
1
a3
+1
=
2
3
+1
=
5
3

故选A.
 
 
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