Discover / combinatorics.openverbs.com

Catalan number

■ Challenge detected

The n-th Catalan number Cₙ = C(2n, n)/(n+1), counting balanced bracketings, binary trees, and many other structures. Requires n ≤ 10000.

x402
Base
USDC

Listed price: $0.004
Challenge detected: 9 of the last 9 checks
Median response: 183 ms
Last checked: 16 Oct, 18:49 UTC
In our index since: 26 Sept 2026

Endpoint

curl -i https://combinatorics.openverbs.com/v1/catalan
# 402 Payment Required: pay with an x402 client (USDC on Base),
# then send the same request again with the payment attached.

5 listed endpoints · on x402 Bazaar

Checks and payment terms on this page refer to the endpoint above. Other listed endpoints have not been checked individually.

Base URLhttps://combinatorics.openverbs.com/v1

POST/multinomial$0.004Multinomial coefficient (k1+k2+…)! / (k1! k2! …) — the number of ways to partition n = Σki items into labelled groups of the given sizes. The sum must be ≤ 20000.
POST/catalan$0.004The n-th Catalan number Cₙ = C(2n, n)/(n+1), counting balanced bracketings, binary trees, and many other structures. Requires n ≤ 10000.
POST/combinations$0.004Binomial coefficient nCr = n!/(r!(n-r)!), the number of unordered r-subsets of n. Requires r ≤ n and min(r, n-r) ≤ 10000.
POST/factorial$0.004Exact factorial n! for 0 ≤ n ≤ 20000, returned as a decimal string with its digit count.
POST/permutations$0.004Number of ordered arrangements of r items from n, nPr = n!/(n-r)!. Requires r ≤ n and r ≤ 10000.

A dash means the listing gives no price or method. Copy buttons copy the full URL.

Showing 5 of 5 listed endpoints.

Agents can find it through the Superstables MCP server and JSON API: GET /api/v1/services/combinatorics.openverbs.com

Recent checks

4 Oct 2026One bar per check, showing up to 20 recent checks. Coloured bars show relative response time, with a minimum visible height; full-height grey bars mean no challenge was detected. “Challenge detected” means HTTP 402 or another detected payment-challenge signal.16 Oct 2026

All 9 checks

When (UTC)	Result	HTTP	Response
16 Oct, 18:49 UTC	Challenge detected	402	180ms
15 Oct, 11:37 UTC	Challenge detected	402	197ms
14 Oct, 00:19 UTC	Challenge detected	402	167ms
12 Oct, 00:34 UTC	Challenge detected	402	183ms
10 Oct, 10:04 UTC	Challenge detected	402	187ms
9 Oct, 06:42 UTC	Challenge detected	402	186ms
8 Oct, 03:32 UTC	Challenge detected	402	163ms
7 Oct, 03:32 UTC	Challenge detected	402	183ms
4 Oct, 05:04 UTC	Challenge detected	402	179ms

Questions

Did our last probe detect a payment challenge?

At our last probe on 16 Oct, 18:49 UTC, it returned HTTP 402 or another detected payment-challenge signal. This check did not test payment, delivery or compatibility with the Superstables client.

What price is recorded for Catalan number?

Its listed price is $0.004.

What payment terms does Catalan number advertise?

The listing advertises x402, Base and USDC. It names cdp as its facilitator. Check the seller's current payment challenge and authentication requirements before paying.

Where is Catalan number listed?

In x402 Bazaar. Superstables first indexed it on 26 Sept 2026.

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