已知以1为首项数列{an}满足: an +1(n为奇数) an+1={an/2(n为偶数)}
问题描述:
已知以1为首项数列{an}满足: an +1(n为奇数) an+1={an/2(n为偶数)}
设数列{an}前n项和为sn,求数列{sn}前n项和Tn
答
A1=1n=1时,A2=A1+1=2n=2时,A3=A2/2=1n=3时,A4=A3+1=2n=4时,A5=A4/2=1..所以 Sn=3n/2 (n为偶数);Sn=3(n-1)/2 +1=(3n-1)/2 (n为奇数)所以 数列{Sn},奇数项是以1为首项3为公差的等差数列,偶数项是以3为首项3为公差的等...