The On-Line Encyclopedia of Integer Sequences (OEIS), created by N. J. A. Sloane, is a database containing nearly 90,000 integer sequences, arranged lexicographically. Each entry includes the initial terms, a description, formulae, programs, references, and links. The database is accessible via the Internet at http://www.research.att.com/~njas/sequences/ and can also be consulted via email. Users can submit sequences or queries, and the system provides detailed information, including references, formulas, and programs. Superseeker, a more advanced tool, performs sophisticated analysis to find explanations for sequences not in the database. The OEIS has its origins in books published in 1973 and 1995. It has grown significantly, with over 72 times more data than the 1995 book. The database is used for identifying sequences, finding current research status, and solving mathematical problems. It is also useful for puzzles, IQ tests, and simplifying complex expressions. The database is maintained by Sloane and a team of associate editors, with a policy of open submission and review. It is used worldwide, with translations available in 28 languages. Sequences must be integer-valued, well-defined, and interesting. They are entered in various formats, including triangular and square arrays. The database includes sequences from combinatorics, number theory, and recreational mathematics, as well as from chemistry and physics. Sequences that are discouraged include those based on arbitrary parameters. The database receives around 10,000 downloads per day and has a steady rate of new submissions. It is used by mathematicians, researchers, and students to find sequences, verify conjectures, and extend existing knowledge. The database is maintained with a focus on accuracy, and users are encouraged to submit sequences they encounter. The OEIS is a vital resource for mathematical research and problem-solving.The On-Line Encyclopedia of Integer Sequences (OEIS), created by N. J. A. Sloane, is a database containing nearly 90,000 integer sequences, arranged lexicographically. Each entry includes the initial terms, a description, formulae, programs, references, and links. The database is accessible via the Internet at http://www.research.att.com/~njas/sequences/ and can also be consulted via email. Users can submit sequences or queries, and the system provides detailed information, including references, formulas, and programs. Superseeker, a more advanced tool, performs sophisticated analysis to find explanations for sequences not in the database. The OEIS has its origins in books published in 1973 and 1995. It has grown significantly, with over 72 times more data than the 1995 book. The database is used for identifying sequences, finding current research status, and solving mathematical problems. It is also useful for puzzles, IQ tests, and simplifying complex expressions. The database is maintained by Sloane and a team of associate editors, with a policy of open submission and review. It is used worldwide, with translations available in 28 languages. Sequences must be integer-valued, well-defined, and interesting. They are entered in various formats, including triangular and square arrays. The database includes sequences from combinatorics, number theory, and recreational mathematics, as well as from chemistry and physics. Sequences that are discouraged include those based on arbitrary parameters. The database receives around 10,000 downloads per day and has a steady rate of new submissions. It is used by mathematicians, researchers, and students to find sequences, verify conjectures, and extend existing knowledge. The database is maintained with a focus on accuracy, and users are encouraged to submit sequences they encounter. The OEIS is a vital resource for mathematical research and problem-solving.