Write the algorithm as a generator so that it outputs the numbers in monotonically increasing order, as required by the answer. Then you can drop successive same counts by using itertools.groupby.

from itertools import groupby
T = int(input())

for _ in range(T):
    n = int(input())
    ab = int(input()), int(input())
    a, b = min(ab), max(ab)

    stonegen = ((n - i - 1) * a + i * b for i in range(n))
    print(*(k for k, g in groupby(stonegen)))

Write the algorithm as a generator so that it outputs the numbers in monotonically increasing order, as required by the answer. Then you can drop successive same counts by using itertools.groupby.

itertools.groupby returns a generator where successive values are pairs (k, g) where k is the key for the group and g is an iterator for the group.

from itertools import groupby
T = int(input())

for _ in range(T):
    n = int(input())
    ab = int(input()), int(input())
    a, b = min(ab), max(ab)

    stonegen = ((n - i - 1) * a + i * b for i in range(n))
    print(*(k for k, g in groupby(stonegen)))