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combinatorics.openverbs.com v1 combinations
https://combinatorics.openverbs.com/v1/combinations
answers 402
Binomial coefficient nCr = n!/(r!(n-r)!), the number of unordered r-subsets of n. Requires r ≤ n and min(r, n-r) ≤ 10000.
We sent a real
POST request to this endpoint and it
answered 402 with payment requirements we could parse.
- Price
- $0.004
- Network
- base
- Pay to
- 0xb3f4de103F34b99f0Da19B4F16D6B53a14C2194A
- Spec dialect
- v2 (declares x402Version 2)
- Transport
- PAYMENT-REQUIRED header
- HTTP method
- POST
- Response latency
- 265 ms
- Payment options
- 1 usable of 1
- Last checked
- 2026-09-06T01:20:10.798Z (23d ago)
- Category
- other
Re-check it yourself:
curl "https://api.the402.dev/validate?url=https%3A%2F%2Fcombinatorics.openverbs.com%2Fv1%2Fcombinations"