The following is a list of some projects that need doing in connection with the
Last major update was in 2005; minor updates Dec 15 2012; Jul 14 2016.
Comments and suggestions for additional entries are welcomed.
%H A002457 < a href= " h t t p : / / m a t h s t a t . c a r l e t o n . c a / ~ z h a o / T E A C H I N G / 7 0 . 2 6 5 / r a n d o m - v / r a n d o m - v . h t m l " >Source< / a >
%H A000396 < a href = " h t t p : / / w w w . u t m . e d u / r e s e a r c h / p r i m e s / m e r s e n n e . s h t m l " >Perfect numbers< / a >
What needs to be done:
Follow every link, make a note of the authors' names and the title of the page, and construct a better link and send it to me. The preferred format is:
%H A060638 M. Latapy, < a href = " h t t p : / / w w w . l i a f a . j u s s i e u . f r / ~ l a t a p y / Z o n o / i n d e x . h t m l " >Tilings of zonotopes< / a >
%H A000396 J. S. McCranie, < a href = " h t t p : / / w w w . r e s e a r c h . a t t . c o m / ~ n j a s / s e q u e n c e s / J I S / i n d e x . h t m l # P 0 0 . 1 . 3 " >A study of hyperperfect numbers, J. Int. Seqs. Vol. 3 (2000) #P00.1.3< / a >
with the author's name first, then the title, etc., inside the link.
The reasons for doing this are: to give more information about the web pages, to give more credit to the authors, and to make these web references have the same format as references to books and journals. There's no reason to distinguish between the different types of references.
If a link is broken, try to find out the correct link, if necessary by contacting the author directly.
What needs to be done:
Scan these journals, books and preprints looking for new sequences or additional references for existing sequences.
Here are some journals that very often contain integer sequences (but which I do not have time to scan):
Suggestions for other journals to add to this list will be welcomed.
When you see a sequence in any of these sources,
send it in using the
Web page for submitting sequences.
Give your name as the author, and give the source in the reference or links
boxes.
Even if you don't fully understand the definition, you can always say something like: "Related to the enumeration of poly-fusenes". Believe me, the next person who comes looking for this sequence will be very grateful for the reference, even if the description is not very precise.
Many university departments, libraries, individuals, etc., publish lists of useful web sites. It would be nice if more of them would mention the On-Line Encyclopedia of Integer Sequences.
What needs to be done:
For any list of "useful sites" or "helpful links" that you can find on the Web, send them a message proposing that they include a link to the OEIS.
Typically the following information is what they need:
Go through
For any sequences discussed in these references, see if there is a formula known for the asymptotic behaviour of a(n) when n is large.
If there is, mention this:
%F A123456 For asymptotic behavior see the article by J. Smith, ...
(and of course add the reference if it is not aleady present).
If the formula is simple enough, then please give it:
%F A123456 For large n, a(n) is asymptotic to 3*2^n - see the article by J. Smith...
Some examples are A056780 A056784 A056841 A056840 A056787 A056844 A056845 A056755 A056843 A056783 A056779 A056785 A056786 A056842 A056769 . What are these sequences? Many of them are taken from web pages like these: Vicher's page, Livio Zucca's page about pentominoes and this one!
What needs to be done? Give a precise definition. Borrow or create a nice picture (as a gif or jpg file, say) to illustrate one of the early terms (see A000105 for an example). Track down similar sequences by following the links in these pages.
Sometimes illustrations can be found on the web.
Often it is possible to get permission to use someone else's
picture. Typically what I do is the following.
Say Jane Smith has a nice web page about caterpillars.
Add a line in the entry for that sequence in the database saying something like:
%H A123456 <a href="http://www.xyz.edu/~smith/">Jane Smith's page about caterpillars.</a>Make a copy of her gif or jpg file that shows the caterpillars of order 4, and link to it by a line like:
%H A123456 <a href="a123456.gif"> Jane Smith's picture of caterpillars of order 4.</a>Of course I ask permission first. I have found that people are usually very willing to cooperate.
The reason I prefer to make a copy of the gif file and put it on the sequence web site, rather than just putting in a link, is that URL's change unexpectedly. Someone said that the average life of a web site is about 6 months. The address of the sequence web site has been unchanged for at least five years.
Thanks to Henry Bottomley (se16(AT)btinternet.com), Vladeta Jovovic (vladeta(AT)Eunet.yu), and others who have contributed illustrations. Much more remains to be done however.
Maybe someone would be willing to look at some of the dead links, and do the detective work necessary to find out if they have moved or if they have been deleted from the Web. If the latter, people are sometimes willing to allow the OEIS to install a copy on the OEIS web site. (Perhaps the person has moved and no longer has a home page of their own.)
The list of bad links as of Dec 13 2000 can be found here.
What needs to be done. For each link on that list:
Thanks mostly to the work of James Sellers (sellersj(AT)math.psu.edu), the list of bad links is now empty. Many thanks, James!
What needs to be done:
Pick one of the standard references that gives lists of binomial coefficient identities.
For a sum that depends on a single parameter n (such as that in A037967 ) convert it into a sequence (and give both sides of the identity).
For a sum with two parameters m and n, convert it into a triangular or square array and hence into a linear sequence by reading the array by rows or by antidiagonals. See the file Welcome to the On-Line Encyclopedia of Integer Sequences for more information about converting arrays into sequences.
If the values of the left- and right-hand sides are integers, then that's the sequence. If they are fractions, then as usual enter the numerators and denominators as separate sequences, with keyword "frac" and linked together by cross-references.
H. W. Gould's "Combinatorial Identities" is the obvious place to start. I have added a handful of sequences from it, but have not gone through it in any systematic way.
Please give references for the binomial coefficient identities that you are using.
Dec. 29, 2000: Many thanks to Yong Kong (ykong(AT)curagen.com), who has sent in many new sequences or comments on existing sequences based on binomial coefficient identities from the book A. P. Prudnikov, Yu. A. Brychkov, and O.I. Marichev, "Integrals and Series", Volume 1: "Elementary Functions", Chapter 4: "Finite Sums", New York, Gordon and Breach Science Publishers, 1986-1992.
D. S. Mitrinovic et al.'s Handbook of Number Theory, Kluwer, is a good source for inequalities in number theory. I have extracted a handful of sequences from it but have not gone through it in any systematic way.
Please give references for any inequalities that you use.
See the files giving the sequences in Comtet's Advanced Combinatorics, Harary and Palmer's Graphical Enumeration and Stanley's Enumerative Combinatorics for examples of such concordances.
What needs to be done: ideally, work through the book, do all the problems, and keep track of all the sequences that occur. (Remember that sequences of rationals numbers are handled by giving separate sequences for the numerators and denominators.)
For each sequence found, make sure it is in the database, and send it in as a new sequence if it isn't, with a reference to the book, of course.
If the sequence is already in the database, check that there is a reference to the book from that sequence, and if there isn't, send that in as a Comment on an existing sequence.
Some books that could be treated in this way are the following. (These are books from which I have already extracted many sequences.)
What needs to be done: Look at all the issues of the appropriate journals, MATCH, Combinatorial Chemistry, J. Math. Chem., etc. Also look for papers in the indexes to the chemical literature for papers with "number of" or "enumeration" in the title or abstract.
Note in particular that Combinatorial Chemistry can be accessed freely if one is a subscriber to ChemDex (and that is also free).
On Dec 13 2000 Elemer Labos (labos(AT)ana1.sote.hu) made the following suggestions:
"Concerning chemical items I know of a group of German and Croatian authors who published a large amount of Computer Generated Organic Molecules ... data (isomer enumeration in the style of Cayley or Polya).
"This was in the Cayley -- Polya tradition. In 1985 they published a lot of isomer enumeration data. Not only trees, rooted trees, physical trees but also condensed hex-es of the most diverse types. I am sure you could find new things in their work.
"A very interesting paper is Knop JV, Mueller WR, Szymanski K, Trinajstic N, Computer generation of certain classes of molecules. SKTH/Kemija u industrij, Zagreb, 1985, 210 pages
"I found Nenad Trinajstic on the Internet as follows:
CROATICA CHEMICA ACTA Editor in Chief - N e n a d T r i n a j s t i c Editor-in-Chief of Croatica Chemica Acta since 1994 N. Trinajstic is a senior scientist at Rudjer Boskovic Institute, full prof. at Faculty of Science , University of Za http://jagor.srce.hr/ccacaa/TRINA.html CROATICA CHEMICA ACTA 72 (1999) No. 1 - CROATICA CHEMICA ACTA 72 (1999) No. 1 Croat. Chem. Acta Vol. 72 No. 1 I-II, 1-133, A1-A63, B1-B5, C1-C6 (1999) Zagreb, March, 1999 CONTENTS Editorial . . . Nenad Trinajstic I-II Physical and http://jagor.srce.hr/ccacaa/co991.html
"I think they would be happy to send you their 1985 publication, including a lot of graphical enumeration data.
"Also I found a coauthor of Trninajstic perhaps in USA ??
DR. EMIL POP'S PUBLICATIONS 1. N. Bodor, E. Pop and N. Trinajstic, "Valence Shell and p Electron SCFMO Calculation for the Isomerism of the 21-Benzylidene-20-oxo-pregnane Derivatives." Rev. Roumaine Chim., 16, 1427-1433 (1971). 2. L. Klasinc, E. Pop, N. Trinajstic and J.V. Knop, "Theoretical Studies of Positional Isomers Obtained by Annelation of Benzene and 5-Membered Ring Heterocyclics Containing N, O or S." Tetrahedron, 28, 3465-3474 (1972). 3. L. Klasinc, N. Trinajstic and E. Pop, "Theoretical Study of Isomeric Thienylfurans." Rev. Roumaine Chim., 18, 89-98 (1973). 4. E. Pop, N. Trinajstic and L. Klasinc, "Theoretical Studies of Some Furocoumarine Isomers." Rev. Roumaine Chim., 18, 1249-1257 (1973). ..... 115. E.Pop, "Water-Soluble Combinations of Dexanabinol: Prodrugs and Analogs", Die Pharmazie, 55, 000-0000 (2000). Contact information: Alchem Laboratories Corp Tel: (904)418-1650 FAX: (904)418-1584 13305 Rachael Boulevard, Alachua, Florida 32615 U.S.A., info(AT)alchem.com
"I think this Dr Pop can give information on how to contcat Trinajstic and get (I am sure in) intersting raw material for EIS.
"Their polyhex isomers seem to me 2D dominoes or animals .
"The German coauthor J.V. Knop was 15 years ago in University of Duesseldorf , Computer Center. I could not find him through the Internet.
[End of quotation]
The keyword "uned", for "unedited", means that I did not have the time to edit the entry in the usual way, which is to:
All such sequences need to be cleaned up.
What needs to be done: for any sequence that has keyword "uned" or "obsc", try to understand the description of the sequence, rewrite the description more clearly and in correct English, and polish up all the other lines in that entry.
%I A037294 %S A037294 2,7,18,42,90,186 %N A037294 Number of (s,2) gates. %D A037294 E Detjens and G Gannot, Technology mapping in MIS, pp. 116-119 of some 1987 IEEE conference proceedings [ # CH2469-5/87 ]. %K A037294 nonn %O A037294 1,1 %A A037294 N. J. A. Sloane (njas(AT)research.att.com).
What needs to be done: pick a topic that interests you and make an index to all the sequences that deal with that topic. For an example, look at the entries under Trees in the index.
Thanks to Christian G. Bower (bowerc(AT)usa.net), Mitch Harris (maharri(AT)cs.uiuc.edu), Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de), and others who have contributed sections to the index. Much more remains to be done however.
What needs to be done:
Update all the incomplete or out-of-date references.
Ideally every reference should give full details. Here is the preferred format:
What needs to be done is to translate the English versions of the current pages into French, and completely redo the French version, making it parallel to the English version.
However, since MathSciNet is a commercial service - and so not accessible to the general public - I don't see hope of doing this at present. Hopefully one day it will be freely available.