He says an attack takes place everyday, with two or three ships taken hostage every week.

VOA: standard.2009.10.30

One over two squared minus one over n squared 3 4 5 where n takes values three, four, five, six.

除以，2，的平方再减去1除以n的平方,将n赋值为。

麻省理工公开课 - 固态化学导论课程节选

n It takes discrete values, multiples of some integer n, and the multiplication factor is the ratio of the Planck constant divided by 2 pi where n takes one, two, three and so on.

这些离散的值乘以整数，乘积因子,是普朗克常数除以2π,其中n可以取1，2，3，等等。

麻省理工公开课 - 固态化学导论课程节选