I won't go into great detail as to why, because most of your eyes will bleed out of your head if I do, but suffice to say, a number of that form is fairly easy to test for primacy.
我不会详细阐述为什么那样， 因为如果我那么做，你们当中的大多数人都会看得眼睛冒血, 我需要说的只是，那种形式的数字 相对容易检验是否是质数。