All combinations from 1 to n of length k in Google Sheets

Question

In Google Sheets, how can I generate a list of the combinations of a given length of numbers between 1 and n?

For example all combinations of length 2 from 1 to 4 would be:

• 1,2
• 1,3
• 1,4
• 2,3
• 2,4
• 3,4