# @cyanheads/oeis-mcp-server

Identify integer sequences by terms, search the OEIS, read formulas, programs, b-files, cross-refs.

- **Type:** MCP server
- **Trust:** 60/100 (B), scored on the package rubric
- **Verification:** community-indexed — nobody has claimed this listing
- **Version:** 0.1.2
- **Author:** io.github.cyanheads
- **License:** Unknown
- **npm:** @cyanheads/oeis-mcp-server
- **Endpoints:** streamable-http https://oeis.caseyjhand.com/mcp
- **Source:** https://github.com/cyanheads/oeis-mcp-server
- **Endpoint health:** reachable (last checked 2026-10-11T15:37:21.928Z, 1 sample) — uptime is not a security property and is not part of the trust score
- **Compatible clients:** claude-code, cursor, copilot, chatgpt, gemini (basis: transport)

## Trust

60/100 (B), scored on the package rubric
- Publisher verified: no
- Install scripts: nothing suspicious found
- Prompt-injection scan: not run
- Obfuscation scan: not run
- Evidence age: 0 days

## Security scan

- **Status:** clean
- **Scanned:** 2026-10-12T15:15:16.581Z
- **Version scanned:** 0.1.2
- **CVEs:** none found by OSV at scan time
**Findings**
- injection-shaped content (note) in the `b-file` tool: Links to undeclared domain: oeis.org

## Tools

40 declared. Statically extracted from the shipped source — a floor on the surface, not a census.
- `oeis-mcp-server`
- `oeis_sequence` — One OEIS entry by A-number as JSON: name, terms, offset, keywords, author, dates, and every section (comments, formulas, examples, programs, references, links, 
- `base` — Depends on the base used to write the numbers.
- `bref` — Too short to analyze.
- `changed` — Changed in the last 2–3 weeks. Set automatically.
- `cofr` — Continued fraction expansion of a number.
- `cons` — Decimal expansion of a constant. The first number of the offset is the number of digits before the decimal point.
- `core` — An important sequence.
- `dead` — Erroneous or duplicated entry; the name points to the correct version, usually by A-number.
- `dumb` — An unimportant sequence.
- `easy` — Easy to produce the terms.
- `eigen` — An eigensequence: fixed under some transform.
- `fini` — A finite sequence.
- `frac` — Numerators or denominators of a sequence of rationals.
- `full` — The full sequence is given (implies fini).
- `hard` — The next term is unknown and hard to find.
- `hear` — Worth listening to as music.
- `less` — Less interesting; less likely to be the sequence being searched for.
- `look` — Has an interesting graph.
- `more` — More terms are needed.
- `mult` — Multiplicative: a(mn) = a(m)a(n) whenever gcd(m,n) = 1.
- `new` — Added or modified in about the last 2 weeks. Set automatically.
- `nice` — An exceptionally nice sequence.
- `nonn` — Every displayed term is nonnegative. Later terms are not guaranteed to be.
- `obsc` — Obscure.
- `probation` — Provisional entry; may be deleted.
- `sign` — Contains negative numbers.
- `tabf` — An irregular triangle, or a fixed-width table, read by rows.
- `tabl` — A regular triangle read by rows, or a square array read by antidiagonals.
- `uned` — Not yet edited.
- `unkn` — Little is known; an unsolved problem.
- `walk` — Counts walks or self-avoiding paths.
- `word` — Depends on the words of some language.
- `allocated` — The A-number is reserved for a sequence not yet published; no data.
- `recycled` — The A-number was freed and is being reused; no published data.
- `paging` — 10 results per page; start takes 0, 10, … 100, so at most 110 results of one query are reachable without an OEIS account.
- `offset` — Written "i,p". i is the index of the first term, so the data line starts at a(i) (1 for a list). p is the 1-based position of the first term with |a(n)| > 1, or
- `b-file` — A text file at https://oeis.org/A######/b######.txt listing "n a(n)" pairs far beyond the data line. oeis_get_terms reads it, one part of up to 1 MiB at a time.
- `referenceCount` — How many OEIS entries mention this A-number, the entry itself included. oeis_get_cross_refs direction incoming lists them.
- `terms` — Every term travels as an exact decimal string; values routinely exceed what a JSON number holds.

## Install

**Verdict: review** — Installable, but 1 thing to check first: No publisher has proved control of this listing; it is indexed, not vouched for.
**Cautions** (coverage gaps and advisories — never blocking)
- No publisher has proved control of this listing; it is indexed, not vouched for.
**Config** (claude-code):
```json
"{\n  \"mcpServers\": {\n    \"oeis-mcp-server\": {\n      \"command\": \"npx\",\n      \"args\": [\n        \"-y\",\n        \"@cyanheads/oeis-mcp-server\"\n      ]\n    }\n  }\n}"
```

## Blast radius

Contained to extensive — no credential declaration found, from the publisher, the upstream registry, or the README. Known so far: runs locally and hosted; read-only tool surface.
- Floor 16, ceiling 34 (tier: unknown)
- `unknown` means the floor and ceiling land in different bands — not measured enough to name one. It does not mean low.
- This is impact, not likelihood. A high radius is not a defect: a filesystem server is supposed to write files. It is never part of the trust score.

## Machine-readable views of this entry

- Signed JSON: https://forgeregistry.com/api/v1/packages/%40cyanheads%2Foeis-mcp-server
- Install plan: https://forgeregistry.com/api/v1/packages/%40cyanheads%2Foeis-mcp-server/install-plan
- Alternatives: https://forgeregistry.com/api/v1/alternatives/%40cyanheads%2Foeis-mcp-server
- HTML page: https://forgeregistry.com/registry/%40cyanheads%2Foeis-mcp-server
- MCP: POST https://forgeregistry.com/api/mcp → `forge_get_package` / `forge_install_plan`

## About this document

Generated by Forge (https://forgeregistry.com) — a compact rendering of the same record served, signed, at the JSON URL above. Trust and scan facts are the registry's own measurements; anything Forge did not measure is named as unmeasured rather than omitted.