a1+an=66,a2an-1=128,Sn=126
a1+an=66,a2an-1=a1 * an =128,
a1=2,an=64;Sn=126,
sn=a1(1-q^n)/(1-q)=2*(2^n-1)=2^7-2=126
n=6,q=2;
或,a1=64,an=2; n=6,q=1/2;