[6]的确是1row*1colomn，但是不是因为不符合matrix的definition，所以不是square matrix？
我找到的答案 就算是 1 row * 1 column 也算是 square matrix
A square matrix is a special type of matrix in which the number of rows is equal to the number of columns. If a square matrix has � n rows and � n columns, it is said to be of the order �n.
Aesthetically, as the name suggests, the matrix looks like a square. Square matrices can be of the order 11, 22 or any number, n�.
参考这里：
https://math.stackexchange.com/questions/685032/can-a-matrix-be-just-1-number#:~:text=Yes%2C%20a%20matrix%20with%20only,one%20column%2C%20i.e.%20one%20entry.
https://www.storyofmathematics.com/square-matrix/
