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GET /v1/combinations

Combinations

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10 free calls per day — no sign-up, no API key. Goes through the oanor gateway.

Custom headers (optional)
api.oanor.com/combinatorics-api

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Code snippets

curl "https://api.oanor.com/combinatorics-api/v1/combinations" \
  -H "x-oanor-key: oanor_test_..."
await fetch("https://api.oanor.com/combinatorics-api/v1/combinations", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
$ch = curl_init("https://api.oanor.com/combinatorics-api/v1/combinations");
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$out = curl_exec($ch);
import requests
requests.get(
    "https://api.oanor.com/combinatorics-api/v1/combinations",
    headers={"x-oanor-key": "oanor_test_..."}
)

Example response

A real response from this endpoint, captured by the latest health check.

{
    "data": {
        "note": "Combinations without repetition: the binomial coefficient nCr = n!/(r!·(n−r)!) unordered selections.",
        "inputs": {
            "n": 10,
            "r": 3,
            "repetition": false
        },
        "formula": "n! / (r!·(n − r)!)",
        "combinations": {
            "exact": "120",
            "digits": 3,
            "approximate": 120
        }
    },
    "meta": {
        "timestamp": "2026-06-05T11:30:31.938Z",
        "request_id": "433627c2-5c4a-4e47-825a-c891aea78961"
    },
    "status": "ok",
    "message": "Combinations",
    "success": true
}