Problem 44476. How many unique Pythagorean triples?

For a given integer n, return all Pythagorean triples that inlude numbers smaller or equal to n.

A Pythagorean triple consist of three positive integers {a, b, c} such that:

 a < b < c,
 a^2 + b^2 = c^2

The triples should be retured in a matrix with tree columns, where each row contains a different triple. Every row needs to be sorted in ascending order ( a in the first column, b in the second and c in the third), and the first column must also be sorted.

Example:

Input:  n   = 16
Output: mat = [3,  4, 5
               5, 12, 13 
               6,  8, 10 
               9, 12, 15]

If n is not an integer, or it is smaller than 5, the function should return an empty matrix.