(a+1)(a的2次方+1)(a的4次方+1)(a的8次方+1)(a的16次方+1)
=(a-1)(a+1)(a的2次方+1)(a的4次方+1)(a的8次方+1)(a的16次方+1)/(a-1)(乘以(a-1)再除以(a-1))
=(a²-1)(a的2次方+1)(a的4次方+1)(a的8次方+1)(a的16次方+1)/(a-1)
=(a的4次方-1)(a的4次方+1)(a的8次方+1)(a的16次方+1)/(a-1)
=(a的8次方-1)(a的8次方+1)(a的16次方+1)/(a-1)
=(a的16次方-1)(a的16次方+1)/(a-1)
=(a的32次方-1)/(a-1)