3nn的知识精选

若数列{an}是正项数列,且++…+=n2+3n(n∈N*),则…+=                    ...
问题详情:若数列{an}是正项数列,且++…+=n2+3n(n∈N*),则…+=                                                         (  )A.2n+2      B.4n+4      C...
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