It depends on what you mean; can there be repeats of numbers? Does order matter? For example...
1111, 1112, 1121, 1211, and 2111 are all different combinations when order doesn't matter and repeats are allowed.
1234, 1243, 1324, 1342, and 1423 are all different combinations when order doesn't matter.
1234, 1235, 1236, 1245, and 1246 are all different combinations when there are no repeats and order matters.