The Wikispecies project lets visitors browse and contribute information about species through its online reference pages.
OEIS
The Online Encyclopedia of Integer Sequences lets visitors search integer sequences and contribute through its community-supported site.
About OEIS
The Online Encyclopedia of Integer Sequences (OEIS) is a searchable database of integer sequences. Its homepage states that it is maintained by The OEIS Foundation Inc. and supported by donors. The homepage lists 400,215 sequences, as of the last-modified date shown there (October 13, 2026).
Visitors can look up sequences with the Lookup tool and can contribute through the site's Contribute section, which requires a login. The interface is available in many languages. The homepage also lists public nominations for sequence A400000.
Key features
- Lookup tool for searching integer sequences
- Contribution section for community submissions to the database
- Registration and login for contributors
- Interface available in many languages, including English, French and Spanish
- Public nominations open for sequence A400000
Best for: Students, researchers and mathematics enthusiasts who need to look up integer sequences or contribute to a community-maintained reference.
Good for
- Contains 400,215 sequences, according to the homepage
- Maintained by The OEIS Foundation Inc. and supported by donors
- Interface offered in many languages
OEIS at a glance
- Website
- oeis.org
- Type
- Website
- Pricing
- Not confirmed. Check the site
- Platforms
- Web
- Open source
- Not stated
- Last checked
- Oct 6, 2026 · Online when checked
- Listed
- Oct 5, 2026
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OEIS FAQ
Who maintains the OEIS?
The homepage states that the OEIS is maintained by The OEIS Foundation Inc. and supported by donors to the OEIS Foundation.
How many sequences does the OEIS contain?
The homepage states that the database contains 400,215 sequences, as of the last-modified date shown there (October 13, 2026).
Is something wrong or out of date?
Tell us and an editor will check it.
Own this website?
Claim this listing
Claim the listing and suggest updates yourself. An editor checks every claim first.