已知等比数列{an}中a1=2,公比q满足lg3*log3(q)=lg2,试写出{an}的通项公式,

题目

已知等比数列{an}中a1=2,公比q满足lg3*log3(q)=lg2,试写出{an}的通项公式,
若bn=a(n)+n,求数列{bn}的前n项和Sn

答案

1.an=2q^(n-1)lg3*log3(q)=lg2log3(q)=lg2/lg3=log3 (2)q=2an=2^n2.bn=a(n)+n=2^n+nSn=[2^1+1]+[2^2+2]+[2^3+3]+……+[2^(n-1)+(n-1)]+[2^n+n]=[1+2+3+……+(n-1)+n]+[2^1+2^2+2^3+……+2^(n-1)+2^n]=(n+1)n/2+2[2^n...