Distinct odd-digit numbers. It means only numbers that comprise of odd digits only.
[(1,), (3,), (5,)] [(1, 3), (1, 5), (3, 1), (3, 5), (5, 1), (5, 3)] [(1, 3, 5), (1, 5, 3), (3, 1, 5), (3, 5, 1), (5, 1, 3), (5, 3, 1)] >>>Total distinct permutations with odd digits only == 15