The On-Line Encyclopedia of Integer Sequences (OEIS) is a web-based searchable database of integer sequences. It is considered one of the major resources in mathematics.

The database

The Encyclopedia is a database recording information on integer sequences that are of interest in mathematics. The database contains over 100000 sequences as of November 2004. Each entry contains the leading terms of the sequence, keywords, mathematical motivations, literature links, and more.

The database is fully searchable, both by keyword and by a subsequence of terms.

Significance

The On-Line Encyclopedia of Integer Sequences is perceived by many as the most authoritative reference in the field of integer sequences. Most work in which such sequences appear (including Wikipedia) contains references to the database.

For professional mathematicians and amateurs alike, OEIS is one of the major online resources in mathematics. It is the largest database of its kind worldwide, and receives thousands of hits per day. Part of its success is no doubt the fact that the database continues to be offered free of charge.

History

Neil Sloane started collecting integer sequences as a student in the mid-1960's to support his work in combinatorics. He published selections from the database in book form twice:

1. A Handbook of Integer Sequences (1973, ISBN 012648550X), containing 2400 sequences.
2. The Encyclopedia of Integer Sequences (1995, ISBN 0125586302), containing 5487 sequences.

These books were highly acclaimed by their audience, and (especially after the second publication) fellow mathematicians supplied Sloane with a steady flow of new sequences. The collection became unmanageable in book form, and when the database had reached 16000 entries Sloane decided to go online—first as an e-mail service (1995), and soon after as a web service (1996). The database continues to grow at a rate of some 10000 entries a year.

Neil Sloane has personally managed 'his' sequences for almost 40 years, but starting 2002 a board of associate editors has helped maintain the database. Volunteers can get involved too.

As a spin-off from the database work, Sloane founded the Journal of Integer Sequences (http://www.math.uwaterloo.ca/JIS/) in 1998.

Papers on OEIS by Neil Sloane

• My Favorite Integer Sequences (http://arxiv.org/PS_cache/math/pdf/0207/0207175.pdf) (2000, PDF file)
• The On-Line Encyclopedia of Integer Sequences (http://www.ams.org/notices/200308/comm-sloane.pdf) (2003, PDF file)

External links

• The On-Line Encyclopedia of Integer Sequences (http://www.research.att.com/~njas/sequences/)