Developer Tool · x402 · early usage

Exact factorial n

Exact factorial n! for 0 ≤ n ≤ 20000, returned as a decimal string with its digit count.

by combinatorics.openverbs.com · discovered, not yet claimed by its owner · updated 2026-10-02

30d calls1

30d payers1

MethodPOST

Outputjson

Mirrored from Coinbase's public x402 Bazaar. The description is the provider's own text and has not been reviewed here; the payment requirements are copied as published.

What it does

Exact factorial n! for 0 ≤ n ≤ 20000, returned as a decimal string with its digit count.

Tags: factorial api · compute factorial · n factorial · exact factorial · bigint factorial · bazaar

Call contract

Method: POST
Input: json
Output: json
Last paid call: 2026-10-02

Input example from Bazaar metadata

{
  "n": "42"
}

No output exampleProvider did not publish one in Bazaar metadata.

Use with an agent

Discover. Agents find this listing with GET https://bazaar.saylorinnovations.com/discovery/search?query=…, the MCP tool search_resources, or /discovery/resources.
Inspect. Fetch /resources/41836.json for the price and payment options.
Pay. Call GET https://combinatorics.openverbs.com/v1/factorial. The provider answers 402 with its payment requirements. An x402 client signs one of the options below and retries with PAYMENT-SIGNATURE.
Execute. The provider returns 200 with the data. Agent Bazaar is not in the request path and never sees your payment.

For humans

You don't need an account or an API key; you need a wallet holding a small amount of USDC on Base, and an x402-capable client (see the examples below). Call the endpoint unpaid first to see exactly what it asks for.

Pricing & payment

Price: $0.004 / request
Protocol: x402 v2
Auth: No account or API key. Pay per request.
Networks: Base
Demand: 1 calls · 1 unique payers in 30d (public x402 Bazaar data)

x402 payment requirements

Scheme	Network	Asset	Amount	Pay to	Timeout
exact	Base eip155:8453	USDC	$0.004	0xb3f4de103F34b99f0Da19B4F16D6B53a14C2194A	300s

accepts[] (raw JSON)

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0xb3f4de103F34b99f0Da19B4F16D6B53a14C2194A",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "4000",
    "amountUsd": 0.004,
    "maxTimeoutSeconds": 300
  }
]

Examples

curl

curl -X POST 'https://combinatorics.openverbs.com/v1/factorial' -H 'Content-Type: application/json' --data '{"n":"42"}'
# -> 402 Payment Required; read PAYMENT-REQUIRED
# retry the identical request with PAYMENT-SIGNATURE

JavaScript

const res = await fetch("https://combinatorics.openverbs.com/v1/factorial", {
  "method": "POST",
  "headers": {
    "content-type": "application/json"
  },
  "body": "{\"n\":\"42\"}"
});
if (res.status === 402) {
  const { accepts } = await res.json();
  // pay one of accepts[] via an x402 client, then retry with the payment header
}

Python

import httpx
import json
res = httpx.request("POST", "https://combinatorics.openverbs.com/v1/factorial", json=json.loads("{\"n\":\"42\"}"))
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header

Details

Provider: combinatorics.openverbs.com
Endpoint: https://combinatorics.openverbs.com/v1/factorial
Machine-readable: /resources/41836.json