在前面乘以 3^2-1 ,再除以 3^2-1 ,原式 = 1/(3^2-1)*[(3^2-1)(3^2+1)(3^4+1)(3^8+1)(3^16+1)(3^32+1)]= 1/8*[(3^4-1)(3^4+1)(3^8+1)(3^16+1)(3^32+1)]= .= 1/8*[(3^32-1)(3^32+1)]= 1/8*(3^64-1)