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Permutations Calculator (nPr)
x402
Permutations Calculator (nPr) is a paid API for AI agents from combinatorics.openverbs.com, paid per call via x402, $0.004/call, status unknown (last checked 2026-09-15).
Computes the number of ordered arrangements of r items chosen from n distinct items using nPr = n!/(n-r)!
Price / call$0.004
Success—
StatusUnknown
How this service works
Number of ordered arrangements of r items from n, nPr = n!/(n-r)!. Requires r ≤ n and r ≤ 10000.
Output
Returns an exact integer (as a large decimal string) representing the number of ordered arrangements of r items selected from n, i.e., nPr = n!/(n-r)!. The result may be a very large number for large inputs.
Example use cases
Ranked contest podium arrangements
“I have 20 athletes competing and I need to award gold, silver, and bronze medals — how many distinct podium orderings are possible? That's choosing 3 from 20 in order.”
Password combination counting
“My system generates ordered PIN codes using 5 digits drawn without repetition from a pool of 12 unique digits — how many distinct PINs are possible? Compute the permutation for n=12, r=5.”
Scheduling ordered interview slots
“I have 8 candidates and I need to fill 3 ranked interview slots in a specific order — first, second, and third. How many ways can I arrange those 3 from my 8 applicants?”
Technical details
Endpoint
POSThttps://combinatorics.openverbs.com/v1/permutationsWhen to prefer
Choose this endpoint when you need the count of ordered selections (permutations) rather than unordered subsets (combinations/nCr). Use it when order matters — e.g., ranking, scheduling, sequencing, or constructing ordered codes. Prefer this over the nCr sibling endpoint when the arrangement sequence is significant. Use the factorial endpoint instead if you need n! directly rather than n!/(n-r)!.
Side effects
- r > n: invalid input since you cannot arrange more items than exist in the set
- r > 10000: exceeds the maximum allowed r value
- n > 1000000: exceeds the maximum allowed n value
- Non-integer or negative values for n or r: schema requires non-negative integer strings
- Missing required fields n or r: returns validation error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object |
Tags
x402
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