The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.



Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

(Greetings from The On-Line Encyclopedia of Integer Sequences!)

The On-Line Encyclopedia of Integer Sequences

The Email Servers and Superseeker

There are two automatic email servers for identifying sequences:

  • The first, sequences@oeis.org, does a simple look-up in the OEIS. Send the message

          lookup 1 2 5 14 42 132 429         [no commas!]

    for example (with no Subject line). Up to 30 sequences can be submitted at the same time.

    The email reply will tell you any sequences in the OEIS (up to a limit of 50) that match your sequence.

    If the word "lookup" does not appear in your message, you will be sent the help file for this server.

    You can also retrieve sequences by A-number -- say
          lookup A12
          lookup A45
          lookup A129

    (However, you can't have both sequence lookups and A-number lookups in the same email message.)

  • The second server, Superseeker, does not just look up the sequence in the OEIS, it will also apply a large number of algorithms in order to attempt to explain the sequence. Send a message to


    containing a line like

    lookup 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

    (with no Subject line). The program will try VERY hard to find an explanation. Only one request may be submitted at a time, and (since this program does some serious computing), only one request per user per hour please. If there is no lookup line you will receive the help file for Superseeker.

Source Code For Email Servers and Superseeker

Click here.

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 7 13:08 EST 2021. Contains 349581 sequences. (Running on oeis4.)