9
There are 6C3 = 20 such combinations.
If repeats are allowed than an infinite number of combinations is possible.
Three combinations: 23, 24 and 34
You can make 5 combinations of 1 number, 10 combinations of 2 numbers, 10 combinations of 3 numbers, 5 combinations of 4 numbers, and 1 combinations of 5 number. 31 in all.
There are 45 combinations.