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API · /sequences-api

Number Sequences API

healthy 3,656 Subscribers

Generate famous integer sequences and test membership, with exact big-integer maths. The generate endpoint returns the first N terms of a sequence — Fibonacci, Lucas, prime numbers, triangular, square, cube, factorial, Catalan, pentagonal and tetrahedral numbers, plus parameterised arithmetic (a start and a step), geometric (a start and a ratio) and powers (any base). The contains endpoint tells you whether a given number belongs to a sequence — is 233 a Fibonacci number, is 21 triangular, is 97 prime, is 720 a factorial — using fast closed-form tests for primes, squares, cubes, triangular, pentagonal and Fibonacci numbers and an exact search for the rest, and it returns the term index where it is known. Because everything is computed with arbitrary-precision integers, terms beyond the usual floating-point limit are returned exactly as decimal strings and never overflow. It runs entirely locally, so it is instant, deterministic and private. Ideal for education and maths tooling, coding challenges and puzzles, test-data generation, recreational mathematics and number-theory experiments. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This generates and tests integer sequences; to factorize a single number or get its divisors use a number-theory API.

#sequences #fibonacci #primes #math #integers #developer-tools
api.oanor.com/sequences-api
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Machine-readable spec so AI agents can integrate this API.

/api/sequences-api/openapi.json
/api/sequences-api/llms.txt

Discovery: GET /api/index.json lists every API.

API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
85 ms
Server probes · 24h
Subscribers
3,656
active
Total calls
57
last 7 days
status Full status page → · 9 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 2,835 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • 2,835 calls/month
  • 2 req/sec
  • 13 sequences + membership
  • No credit card
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Starter

€4.35 /month

  • 12,350 calls / month
  • 8 requests / second
  • Hard cap (429 above quota, no overage)
  • 12.35k calls/month
  • 8 req/sec
  • Exact big-integer terms
  • Email support
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Pro

€24.25 /month

  • 174,500 calls / month
  • 20 requests / second
  • Hard cap (429 above quota, no overage)
  • 174.5k calls/month
  • 20 req/sec
  • Education / puzzle / test-data pipelines
  • Priority support
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Mega

€62.25 /month

  • 915,000 calls / month
  • 50 requests / second
  • Hard cap (429 above quota, no overage)
  • 915k calls/month
  • 50 req/sec
  • Platform scale
  • Dedicated SLA
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Related APIs

Other APIs with overlapping tags.

Fibonacci Levels API

Automatic Fibonacci retracement and extension levels for any stock, index, FX pair, commodity or crypto, computed live from Yahoo Finance candles, no key. Fibonacci levels are the support/resistance map traders draw from a trend's swing high and swing low: after a move, price tends to pull back to the 38.2%, 50% or 61.8% retracement before resuming, and to project to the 127.2%, 161.8% or 261.8% extension as a target. This finds the dominant recent swing automatically and lays the levels out, with where price sits right now. The retracement endpoint detects the swing high and low over a lookback window, works out the trend direction, and returns the retracement levels (0, 23.6, 38.2, 50, 61.8, 78.6, 100%) with their prices — plus which two levels price is currently between and the nearest one. The extension endpoint returns the projection targets beyond the swing (127.2, 141.4, 161.8, 200, 261.8%) in the trend's direction. Both report the swing they were built from so you can see exactly what was measured. This is the Fibonacci-levels cut — a distinct price-level tool, separate from the oscillator and channel indicator feeds (RSI, MACD, Bollinger, SuperTrend, Keltner), from FX pivot points and from the Ichimoku system. Levels are in the instrument's own price; the swing is detected mechanically (highest high / lowest low over the window), not hand-picked. Interval (1d/1wk/1mo) and lookback are configurable. Keyless, nothing stored beyond a short cache.

api.oanor.com/fibonacci-api

Number Theory API

An integer toolkit as an API. Factorize any number into its prime factors with exponents (and a readable 2^3 × 3^2 × 5 form), with the divisor count, the divisor sum, the full list of divisors and whether the number is perfect; find the greatest common divisor and least common multiple of two numbers (and whether they are coprime); and test primality, returning the next and previous prime. Handles numbers up to a trillion. Perfect for maths education and puzzles, cryptography demos, generating test data and any time you need the building blocks of a number. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 4 endpoints. A focused integer toolkit, distinct from a general math-expression engine.

api.oanor.com/numbertheory-api

Combinatorics API

Combinatorics maths as an API, computed locally and deterministically with exact arbitrary-precision integers. The factorial endpoint computes n! = 1·2·3···n (with 0! = 1) and returns it exactly as a string together with its digit count, so even very large factorials stay precise. The permutations endpoint counts ordered arrangements: without repetition nPr = n!/(n−r)! arrangements of r items chosen from n, and with repetition n^r, where each of the r positions may be any of the n items. The combinations endpoint counts unordered selections: without repetition the binomial coefficient nCr = n!/(r!·(n−r)!), and with repetition (multisets) C(n+r−1, r), where repeats are allowed. All results are computed with BigInt so they are exact no matter how large, returned as a string with the number of digits and a floating-point approximation when it fits. n and r are non-negative integers up to 100000. Everything is computed locally and deterministically, so it is instant and private. Ideal for probability, statistics, lottery, game-design, cryptography and education app developers, counting and odds tools, and discrete-maths teaching. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is counting combinatorics; for modular arithmetic use a modular API and for descriptive statistics a statistics API.

api.oanor.com/combinatorics-api

Modular Arithmetic API

Modular-arithmetic maths as an API, computed locally and deterministically with exact big-integer arithmetic. The power endpoint computes modular exponentiation, aᵇ mod m, by square-and-multiply, fast and exact even for the huge exponents used in cryptography. The inverse endpoint finds the modular multiplicative inverse a⁻¹ mod m with the extended Euclidean algorithm, returning the inverse when a and m are coprime and reporting the gcd when no inverse exists. The totient endpoint computes Euler's totient φ(n) — the count of integers from 1 to n coprime to n — with the prime factorization it comes from, and an optional Euler-theorem check that a^φ(n) ≡ 1 (mod n) for a coprime base. These are the building blocks of RSA and much of modern cryptography. Inputs are integers and can be passed as strings for very large values. Everything is computed locally and deterministically, so it is instant and private. Ideal for cryptography, security, blockchain and mathematics app developers, RSA and number-theory tools, and computer-science education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is modular arithmetic; for prime factorization and GCD use a number-theory API and for integer sequences a sequences API.

api.oanor.com/modular-api

Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Number Sequences API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Number Sequences API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Number Sequences API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does Number Sequences API cost?
Number Sequences API has a free tier with 100 calls / month. Paid plans start at €4.35 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is Number Sequences API GDPR-compliant?
All requests to Number Sequences API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.

Pick an endpoint from the list on the left to see its details and try it.

Code snippets

Sign up to get an API key, then call any path under your slug.

curl https://api.oanor.com/sequences-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/sequences-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/sequences-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);
import requests
r = requests.get(
    "https://api.oanor.com/sequences-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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