a11Sn的精選

問題詳情：已知數列{an}的前n項和為Sn,且a1=1,Sn=,則a2017=()A.2016          B.2017       C.4032          D.4034【回答】B∵a1=1,Sn=,∴當n≥2時,an=Sn-Sn-1=,可化為,∴=…==1,∴an=n....