先把n=1代入,可得a1=1/2,再把n=2再入,可得3a2=1/2,n每增加1,多一项,且和多1/2,所以每一项都是1/2,所以3的n-1次方an=1/2,an=1/(2*3的n-1次方).
已知数列an满足a1+3a2+3²a3+……+3的n-1次方an=n/2,则an=
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