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已知数列{an},满足a1=1,an=a1+2a2+3a3+…+(n-1)an-...
已知数列{an},满足a1=1,an=a1+2a2+3a3+…+(n-1)an-1(n≥2),则{an}的通项 .
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a
2+b
2=1,b
2+c
2=2,c
2+a
2=2,则ab+bc+ca的最小值为( )
A.
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B.
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C.-
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D.
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