# io.github.cyanheads/oeis-mcp-server

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

- name: io.github.cyanheads/oeis-mcp-server
- version: 0.1.3
- connection class: R0 (autonomous)
- trust: 94/100
- quality: 89/100 (good)
- owner: not claimed
- descriptor: https://api.protogrid.dev/v1/servers/io.github.cyanheads%2Foeis-mcp-server
- tools: https://api.protogrid.dev/v1/servers/io.github.cyanheads%2Foeis-mcp-server/tools

**An agent can connect right now, no human step.** Remote endpoint, no authentication, reachable on the last probe.

## Connection (mcpServers)

```json
{
  "mcpServers": {
    "oeis-mcp-server": {
      "type": "http",
      "url": "https://oeis.caseyjhand.com/mcp"
    }
  }
}
```


## Trust

- hygiene: 100
- liveness: 100
- freshness: 100
- provenance: 80
- drivers: +repository +namespace-matches-repo +reachable +uptime-100% +updated-2d-ago
- Derived from observable signals (official registry feed and our own credential-free probes); no code audit performed.

## Quality 89/100 (good)

### protocol: 88 (weight 25)

- pass `protocol.modern`: supports 2026-07-28 (server/discover)
- pass `protocol.stateless`: answers without a session
- pass `protocol.transport`: streamable HTTP
- warn `protocol.list_ttl`: tools/list declares ttlMs 0, so clients re-fetch it on every use

### authorization: n/a (weight 15)

- n/a `auth.prm`, `auth.as_metadata`, `auth.cimd`: no remote uses OAuth
- n/a `auth.secret_in_url`: no templated URL

### tool hygiene: 86 (weight 30)

- pass `tools.descriptions`: every tool has a description
- pass `tools.description_length`: descriptions are concise
- pass `tools.schemas`: every tool has an object input schema
- pass `tools.annotations`: 6 of 6 tools declare readOnlyHint or destructiveHint
- fail `tools.directory_hints`: no tool declares all four of readOnlyHint, destructiveHint, idempotentHint and openWorldHint; missing: oeis_identify_sequence (destructiveHint); oeis_search_sequences (destructiveHint); oeis_get_cross_refs (destructiveHint); …
- pass `tools.token_cost`: about 2,188 tokens to load every tool
- pass `tools.api_dump`: tools are not a one-to-one API dump

### stability: 100 (weight 15)

- pass `stability.changes`: 2 tool changes in 30 days
- pass `stability.rug_pull`: no tool changed its meaning under the same name

### dependencies: n/a (weight 15)

- n/a `deps.known_vulns`, `deps.mcp_sdk_version`, `deps.resolvable`: deps.dev does not know @cyanheads/oeis-mcp-server@0.1.3, @cyanheads/oeis-mcp-server@0.1.3

- tools: 6, about 2,188 tokens to load them all
- tool set hash: d62f821394ad2ee2e76c7f2c23650b2c
- tools last changed: 2026-10-18T11:40:16.132Z
- badge: [![protogrid quality](https://protogrid.dev/badge/io.github.cyanheads/oeis-mcp-server.svg)](https://protogrid.dev/servers/io.github.cyanheads/oeis-mcp-server)
- Checks run on what our credential-free, read-only probes observe; tools are never called and no code audit is performed.

### Tool changes

- 2026-10-18 `oeis_get_terms` changed (description, inputSchema, outputSchema)
  - before: List terms a(n) of a sequence with their indices n. Reads the entry's b-file when it has one — often thousands of terms beyond the data line — and otherwise the data line itself. Values are exact decimal strings of any size. A slice stops at limit terms, at about 100,000 bytes, or at the end of one 1 MiB part of a larger b-file, whichever comes first; nextFromIndex continues it.
  - after: List terms a(n) of a sequence with their indices n. Reads the entry's b-file when it has one — often thousands of terms beyond the data line — and otherwise the data line itself. Values are exact decimal strings of any size. A slice stops at limit terms (at most 1000 per call), at about 100,000 bytes, or at the end of one 1 MiB part of a larger b-file, whichever comes first; nextFromIndex continues it.
- 2026-10-18 `oeis_search_sequences` changed (inputSchema, outputSchema)

Full history: https://api.protogrid.dev/v1/servers/io.github.cyanheads%2Foeis-mcp-server/changes

## Dependencies

- npm @cyanheads/oeis-mcp-server@0.1.3: unknown
- npm @cyanheads/oeis-mcp-server@0.1.3: unknown

Dependency graphs from deps.dev; advisories from OSV.dev, including the GitHub Advisory Database and the PyPI Advisory Database; all CC BY 4.0.

## Remotes

- https://oeis.caseyjhand.com/mcp (streamable-http, auth none, reachable true, uptime30d 1)

## Packages

- npm @cyanheads/oeis-mcp-server@0.1.3
- npm @cyanheads/oeis-mcp-server@0.1.3

## Tools (6)

- `oeis_get_cross_refs`: List sequences related to an OEIS entry. direction outgoing returns the A-numbers named in the entry's cross-reference (Cf.) lines, with any parenthetical note beside each; direction incoming returns entries that mention this A-number anywhere. Each row carries the related sequence's name and first terms. 10 rows per page.
- `oeis_get_sequence`: Fetch one OEIS entry by A-number. Returns the name, data-line terms, offset, keywords, author, dates, and the sections: comments, formulas (recurrences and generating functions), examples, programs (Maple, Mathematica, PARI, Python, …), references, links, cross-references, and extensions. When the sections together exceed 24,000 characters of serialized JSON, the core fields come back with a section outline instead; call again with sections to pick what to read. A selection past 100,000 bytes comes back in parts cut between items: pass nextFromItem as fromItem, with the same sections, for the next part.
- `oeis_get_terms`: List terms a(n) of a sequence with their indices n. Reads the entry's b-file when it has one — often thousands of terms beyond the data line — and otherwise the data line itself. Values are exact decimal strings of any size. A slice stops at limit terms (at most 1000 per call), at about 100,000 bytes, or at the end of one 1 MiB part of a larger b-file, whichever comes first; nextFromIndex continues it.
- `oeis_identify_sequence`: Identify integer sequences that contain a run of consecutive terms, e.g. "1, 2, 5, 14, 42". Returns up to 10 matches per page in OEIS relevance order, each with the index n at which the supplied run begins. For the best hit rate supply about 6 terms and leave off the first one or two, since sources disagree on where a sequence starts. OEIS matches only the first terms of each entry (its data line, at most about 270 characters), not its b-file, so a run from far into a sequence is not found. Takes up to 60 terms, each an integer of at most 200 digits or the wildcard _ for one unknown term.
- `oeis_list_reference`: Look up OEIS vocabulary used by the other tools: keyword flags (nonn, core, tabl, cons, …), search syntax (prefixes, operators, wildcards, sort orders, paging window), and identifier conventions (A-numbers, legacy M/N numbers, offsets, b-files).
- `oeis_search_sequences`: Search the OEIS using its query syntax: plain words, "quoted phrases", comma-separated terms, prefixes (keyword:, author:, name:, comment:, formula:, program:, xref:, id:), | for OR, and a leading - to exclude. Returns up to 10 summaries per page. For identifying a sequence from its terms, oeis_identify_sequence is the direct route.