有關a1a2a2a3的精選大全

數列{an}滿足a1=,a2=,且a1a2+a2a3+…+anan+1=na1an+1對任何正整數n成立,則+...
問題詳情:數列{an}滿足a1=,a2=,且a1a2+a2a3+…+anan+1=na1an+1對任何正整數n成立,則++…+的值為     .【回答】85 解法一:由a1a2+a2a3=2a1a3及a1=,a2=,得a3=,再由a1a2+a2a3+a3a4=3a1a4,a4=.進一步得a5=,a6=,a7=,a8=,a9=,a10=,故++…+=4+5+6+7+8+9+10+11...
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