a1+an=66a2*an-1=a1*an=128所以可得：a1=2,an=64或a1=64,an=2当a1=2,an=64时有：Sn=a1(1-q^n)/(1-q)=(a1-anq)/(1-q)=(2-64q)/(1-q)=126解得：q=2q^(n-1)=an/a1 即：2^(n-1)=32 所以可得：n=6当a1=64,an=2时有：Sn=a1...