# Python >= 3.9
def square(n: int) -> list[list[float]]:
from itertools import permutations
from random import random
matrix = [list([0]*n) for _ in range(n)]
total = 0.0
for index in permutations(range(n)):
value = random()
total += value
for i, j in enumerate(index):
matrix[i][j] += value
return [[elem / total for elem in row] for row in matrix]