a11Sn的精选

问题详情：已知数列{an}的前n项和为Sn,且a1=1,Sn=,则a2017=()A.2016          B.2017       C.4032          D.4034【回答】B∵a1=1,Sn=,∴当n≥2时,an=Sn-Sn-1=,可化为,∴=…==1,∴an=n....