其根本原因就在于：调和级数去掉若干项后剩余下的项数相对于原调和级数的项数是否为一个低阶的无穷大。
What the most basic reason is: whether the progression's remainders are infinity, compared to its lower one, after the removal of its amount of items.
证明不存在四个连续的二项系数成算术级数。
Prove that no four consecutive binomial coefficients can be in arithmetic progression.
在三缝的情况下，对通过3个缝隙的波相互之间的干涉计算会产生三项级数。
In the case of three slits, the calculation produces three terms describing interference between waves travelling through the three possible pairs of slits.
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