From the mathematics article 拉丁阵的枚举和计数(Ⅱ):情形n=4,k〈=4, we have the following first paragraph:
I'm confused about what 合痕类的个数 (hé hén lèi de gè shù) means here (it's used twice). Google Translate says it means "the number of traces", but I don't feel this is accurate.
Question: What does 合痕类的个数 (hé hén lèi de gè shù) mean in this mathematics article?
In document  is the fascinating引人 (short for 引人入胜 (?)) concept概念 of the (n,k)-Latin matrix, and the case情形 of n=2,3, gives (n,k)-Latin matrices and their [合痕类的个数 (?)]. In this paper, we continue继续 the discussion讨论 to the case情形 of n=4, give (4,k,1)-Latin matrices, (4,2), (4,3), and (4,4)-Latin matrices and their [合痕类的个数 (?)].
If it helps, here's an example of what one looks like: