Math python question

[lothar]

my interpreation of this task:

from itertools import permutations

res = []
nums = [1,2,3,4]
not_allowed = [(1,2),(2,3),(3,4)]

for perm in permutations(nums,2):
    if perm not in not_allowed:
        res.append(perm)
print(res)

Output:
[(1, 3), (1, 4), (2, 1), (2, 4), (3, 1), (3, 2), (4, 1), (4, 2), (4, 3)]