(n+1)a(n+1)=nan
a(n+1)/an=n/(n+1)
a(n+1)/an=n/(n+1)
an/a(n-1)=(n-1)/n
.
a3/a2=2/3
a2/a1=1/2
以上等式相乘得
a(n+1)/a1=1/(n+1)
a(n+1)/2=1/(n+1)
a(n+1)=2/(n+1)
an=2/n
(n+1)a(n+1)=nan
a(n+1)/an=n/(n+1)
a(n+1)/an=n/(n+1)
an/a(n-1)=(n-1)/n
.
a3/a2=2/3
a2/a1=1/2
以上等式相乘得
a(n+1)/a1=1/(n+1)
a(n+1)/2=1/(n+1)
a(n+1)=2/(n+1)
an=2/n