Positive compositions (each part at least 1) (Number of ways to write n as sum of r positive integers (order matters))
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Number of ways to write n as sum of r positive integers (order matters): C(n−1, r−1)
What each symbol means
| Symbol | What it stands for |
|---|---|
| n | Total sum |
| r | Number of positive summands |
When to use this
Requires n ≥ r so each part can be at least 1.