How many combinations for numbers 1248?

With 4 digits you can have 24 = 16 combinations.

1 combination with 0 digits;

4 combinations with 1 digit: 1, 2, 4 and 8

6 combinations with 2 digits: 12, 14, 18, 24, 28 and 48

4 combinations with 3 digits: 124, 128, 148 and 248

1 combination with all 4 digits.

In a combination the order of digits is not relevant so that 124 is the same as 142.