how to compute transition in a N X N matrix where the dimensions are not not sequential

Question

I have the following data:

import numpy as np
import pandas as pd


arr = np.array([0, 1, 2, 3, 4, 6, 7, 5])
x = pd.Series([0,1,2,3,4,6,7,0,1,2,3,4,6,7,0,1,2,3,4,