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io.github.cyanheads/oeis-mcp-server

by cyanheads · remote · local (npm) · no sign-in to list tools · v0.1.3 · published by GitHub user cyanheads

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

Changes · 1
CompareRegistry entry

6 tools: 1 change things and 5 only read.

Scanned Oct 21, 2026

No check matched anything in the tool definitions. No finding is not a safety guarantee. How the checks work.

claude mcp add --transport http oeis https://oeis.caseyjhand.com/mcp

Tools

Open a tool for its reasons and full description. Descriptions are the publisher's own words, shown as they are.

6 tools

Changes things 1Claude Code: ask
  • oeis_identify_sequenceIdentify integer sequences that contain a run of consecutive terms, e.g.No findings

    Why it is in this group

    • Nothing in its name or description says what it does, so it is counted as a write.
    • The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.
    Description, as the server wrote it
    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.

    Annotations the server declares

    • readOnlyHint: true
    • idempotentHint: true
    • openWorldHint: true
Only reads 5Claude Code: allow
  • oeis_get_cross_refsList sequences related to an OEIS entry.No findings

    Why it is in this group

    • The name "oeis_get_cross_refs" says "get": a word for reading.
    Description, as the server wrote it
    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.

    Annotations the server declares

    • readOnlyHint: true
    • idempotentHint: true
    • openWorldHint: true
  • oeis_get_sequenceFetch one OEIS entry by A-number.No findings

    Why it is in this group

    • The name "oeis_get_sequence" says "get": a word for reading.
    Description, as the server wrote it
    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.

    Annotations the server declares

    • readOnlyHint: true
    • idempotentHint: true
    • openWorldHint: true
  • oeis_get_termsList terms a(n) of a sequence with their indices n.No findings

    Why it is in this group

    • The name "oeis_get_terms" says "get": a word for reading.
    Description, as the server wrote it
    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.

    Annotations the server declares

    • readOnlyHint: true
    • idempotentHint: true
    • openWorldHint: true
  • oeis_list_referenceLook up OEIS vocabulary used by the other tools: keyword flags (nonn, core, tabl, cons, …), search syntax (prefixes, operators, wildcards, sort orders, paging window), and identifi…No findings

    Why it is in this group

    • The name "oeis_list_reference" says "list": a word for reading.
    Description, as the server wrote it
    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).

    Annotations the server declares

    • readOnlyHint: true
    • idempotentHint: true
    • openWorldHint: false
  • oeis_search_sequencesSearch the OEIS using its query syntax: plain words, "quoted phrases", comma-separated terms, prefixes (keyword:, author:, name:, comment:, formula:, program:, xref:, id:), | for O…No findings

    Why it is in this group

    • The name "oeis_search_sequences" says "search": a word for reading.
    Description, as the server wrote it
    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.

    Annotations the server declares

    • readOnlyHint: true
    • idempotentHint: true
    • openWorldHint: true

This is not a safety rating, and no finding is not a safety guarantee. The groups and findings come from fixed checks of the tool definitions the server returned on the date shown, not from its code or what it does when called. How the checks work.

Install

Pinned to version 0.1.3. Values in angle brackets are yours to fill in.

claude mcp add --transport http oeis https://oeis.caseyjhand.com/mcp

Run in a terminal.

Claude Code permissions

Allow the reads, ask before a change, deny the deletes. Paste into .claude/settings.json.

.claude/settings.json
{
  "permissions": {
    "allow": [
      "mcp__oeis__oeis_search_sequences",
      "mcp__oeis__oeis_get_sequence",
      "mcp__oeis__oeis_get_terms",
      "mcp__oeis__oeis_get_cross_refs",
      "mcp__oeis__oeis_list_reference"
    ],
    "ask": [
      "mcp__oeis__oeis_identify_sequence"
    ],
    "deny": []
  }
}

Tools that only read are allowed, tools that change things ask first, tools that delete or cancel are denied. It assumes the server is installed as oeis. Review it before you use it.