设数列{an}的前n项和为Sn,若a1=1,Sn=2an+Sn+(n∈N+),则a6=

问题描述:

设数列{an}的前n项和为Sn,若a1=1,Sn=2an+Sn+(n∈N+),则a6=

应该是“Sn=2an+Sn-1”吧?