Sequences That Need Extending

Sequences That Need Extending

Want to help? Many sequences in the
the On-Line Encyclopedia of Integer Sequences
need extending!

• ===Extending Sequences===IMPORTANT: Thousands of people use the sequence database every day.
  Please take great care that the terms you send are absolutely correct.
  The standards are those of a mathematics reference work. These sequences need extending.If possible please use the [[<dont>|form]] when sending extensions or comments.For other ways in which you could help, please see the List of Future Projects
• ===Sending in an extension.===
  • If possible please use the [[<dont>|form]] when sending extensions or comments.
  • Ideally I would like to get enough terms for each sequence to fill about three lines on the screen. Failing that even a single extra term is always welcome.
  • Please be sure to specify the sequence number in any message.
  • It is also a good idea to give the first few terms as well as the terms before that come before the new terms, to avoid any confusion. It is very easy to type A045912 when you mean A049512, and giving the first few terms of the sequence helps to detect such errors!
• ===What will be needed.===
  • Some of these sequences can be calculated from the formula, recurrence or generating function given in the description.
  • Other sequences will require going to a library, to look up the formula or recurrence given in the references for the sequence (sometimes a reference will explicitly list more terms, which the person who contributed the sequence did not copy down).
  • Some sequences will require that you write a program to work them out - for instance to count the structures of a certain kind.
  • Some of the sequences will be very hard to extend. On the other hand there's more glory in extending them.
  • All contributions will be acknowledged.
• ===Computer programs.=== If you can generate the sequence with a few lines of code in one of the standard languages, please send the program too. I am trying to give computer code to generate sequences whenever possible.
• ===Updates.===
  • The database is usually updated every few days, often every day, so if you are working on a sequence for a while, it is a good idea to recheck it to make sure no one else has extended it. This file is automatically updated with the main table.
  • Please send email to njas@research.att.com if there is a sequence on the above list that should not be there - for example if there are already enough terms to fill three lines, if no more terms exist in the sequence, or if the next term is more than 10^80.
• ===Other problems.=== See if you can improve any of the known lower bounds on constant weight codes. Many of them are extremely weak!