(Ⅰ)由题意可得,公比q≠1,再由S3=
,S6=7 2
可得 63 2
,
=
a1(1-q3) 1-q
7 2
=
a1(1-q6) 1-q
63 2
解得
,故通项公式为 an=
a1=
1 2 q=2
?2n-1=2n-2.1 2
(Ⅱ)由(Ⅰ)可得log2an=n-2,
∴log2a1+log2a2+log2a3+…+log2a25
=-1+0+1+2+…+23
=
25(-1+23) 2
=275.