# How to cite a sequence from The On-Line Encyclopedia of Integer Sequences (OEIS)?

In my paper I want to provide a reference for a sequence (in this case - A001970) from The On-Line Encyclopedia of Integer Sequences (OEIS).

However, I couldn't find an official bib entry for it (there is an unofficial OEIS2BibTeX). Even the respective FAQ/Wiki entry is a bit vague on the issue, providing only a suggestion:

A text reference might say:

The On-Line Encyclopedia of Integer Sequences, published electronically at http://oeis.org, 2010, Sequence A000108

or, if it is clear who "discovered" the sequence, something like

J. H. Conway, Sequence A007970 in The On-Line Encyclopedia of Integer Sequences (2010), published electronically at http://oeis.org.

Moreover, in most of papers I saw people add N. [J. A.] Sloane but drop the year, e.g.:

N. J. A. Sloane, The On-Line Encyclopedia of Integer Sequences, Sequence A000009.

So, is there a "good practice" for citing OEIS sequences?

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## 2 Answers

To answer the question briefly: if you didn't find a guide or enough examples of a good practice online, then it is underpromoted (which includes the possibility that it doesn't exist).

People are still working on ways to cite online material, especially when referring to evolving resources like MathOverflow. If you can provide enough reference points in the bibliography to ensure that anyone who checks will find that to which you refer, then you have done your part of the job. MathOverflow assists in this by providing static unmodifiable data (question number, user number, timestamp of revision, etc.) as well as a link that gives you the data in a format suitable for bibliographic reference, but that is no guarantee that things won't change after some transition.

If OEIS had made some suggestion for reference which you still find wanting, I offer two: For the short term (while you are still active), prepare an electronic file which contains additional research notes for limited distribution. This can include your favorite online resource links or even gossip about which reference librarians to ask, but one thing it can include is a jpeg which is a screen snapshot of the OEIS page as it looked when you retrieved it. That way, for any future researcher who can't verify that part of your work and asks something like "What choo talking about Willis?", you can send them jpeg as supporting material. Hopefully they will still have a jpeg reader in that decade.

For the rest of posterity, also include links to other papers which use the sequence. Future historians can then infer the existence of a great and powerful database, something like a lost continent, which was gifted to mankind for the purpose of furthering intellectual acheivements, and which may inspire them to reconstruct it from whatever digital archives the insect rulers left to them.

Gerhard "Needs Some New Science Fiction" Paseman, 2013.05.20

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In theory, a (hidden) inline may be a good option (to make it clear, self-contained and as now we don't need to pay for paper and ink). Sure, for it is also a boon to archeologists discovering our civilization. I am aware of some dangers (even the previous (i.e. research.att.com/~njas/sequences) link to OEIS is not working), but otherwise numbering seems to be consistent and I want to provide only a reference, not use it as a detailed argument. –  Piotr Migdal May 20 '13 at 21:48
That said, the question is "what to do?" in a practical case, where I can write a line of a reference (as for other articles and books). –  Piotr Migdal May 20 '13 at 22:08
You could do worse than mimic references for MathOverflow. Doing a full-text search in arXiv yields many examples, one of which is 1207.1020 involving nilpotency of finite groups. That suggests something like "This sequence appears in OEIS" (or "in Sloane's database") " as A001970 [OEIS1970]...", followed by a bibitem that would be something nicer than "[OEIS1970] Online Encyclopedia of Integer Sequences, Sequence A001970, oeis.org/search?A001970 , N. J. A Sloane ... 2013." Gerhard "Ask Me About System Design" Paseman, 2013.05.20 –  Gerhard Paseman May 20 '13 at 22:41
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Just for a reference, I did cite it as:

N. J. A. Sloane. The On-Line Encyclopedia of Integer Sequences, http://oeis.org. Sequence A001970.

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Looks good to me. Gerhard "Insect Rulers Might Also Approve" Paseman, 2013.05.21 –  Gerhard Paseman May 21 '13 at 17:12
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