1.1/3.1/7.1/13,1/21求通项公式
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1.1/3.1/7.1/13,1/21求通项公式
1.1/3.1/7.1/13,1/21
求通项公式
1.1/3.1/7.1/13,1/21求通项公式
1,1/3,1/7,1/13,1/21
for n>=2
1/an - 1/a(n-1) = 2(n-1)
1/an - 1/a1 = 2[ 1+2+...+(n-1) ]
=n(n-1)
1/an = n^2-n+1
an = 1/(n^2-n+1)