It's almost February in 2018, which isn't supposed to be the proper time to cycle these, but for this year it'll be once again, so we'll be refreshing the Community Promotion Ads for this year now!

What are Community Promotion Ads?

Community Promotion Ads are community-vetted advertisements that will show up on the main site, in the right sidebar. The purpose of this question is the vetting process. Images of the advertisements are provided, and community voting will enable the advertisements to be shown.

Why do we have Community Promotion Ads?

This is a method for the community to control what gets promoted to visitors on the site. For example, you might promote the following things:

  • the site's twitter account
  • useful tools or resources for the mathematically inclined
  • interesting articles or findings for the curious
  • cool events or conferences
  • anything else your community would genuinely be interested in

The goal is for future visitors to find out about the stuff your community deems important. This also serves as a way to promote information and resources that are relevant to your own community's interests, both for those already in the community and those yet to join.

Why do we reset the ads every year?

Some services will maintain usefulness over the years, while other things will wane to allow for new faces to show up. Resetting the ads every year helps accommodate this, and allows old ads that have served their purpose to be cycled out for fresher ads for newer things. This helps keep the material in the ads relevant to not just the subject matter of the community, but to the current status of the community. We reset the ads once a year, every December.

The community promotion ads have no restrictions against reposting an ad from a previous cycle. If a particular service or ad is very valuable to the community and will continue to be so, it is a good idea to repost it. It may be helpful to give it a new face in the process, so as to prevent the imagery of the ad from getting stale after a year of exposure.

How does it work?

The answers you post to this question must conform to the following rules, or they will be ignored.

  1. All answers should be in the exact form of:

    [![Tagline to show on mouseover][1]][2]
       [1]: http://image-url
       [2]: http://clickthrough-url 

    Please do not add anything else to the body of the post. If you want to discuss something, do it in the comments.

  2. The question must always be tagged with the magic tag. In addition to enabling the functionality of the advertisements, this tag also pre-fills the answer form with the above required form.

Image requirements

  • The image that you create must be 300 x 250 pixels, or double that if high DPI.
  • Must be hosted through our standard image uploader (imgur)
  • Must be GIF or PNG
  • No animated GIFs
  • Absolute limit on file size of 150 KB
  • If the background of the image is white or partially white, there must be a 1px border (2px if high DPI) surrounding it.

Score Threshold

There is a minimum score threshold an answer must meet (currently 6) before it will be shown on the main site.

You can check out the ads that have met the threshold with basic click stats here.

  • 1
    Shouldn't there be a recommendation to provide a text version of the ad in the comments, for searchability? – Samuel Lelièvre Aug 1 at 11:31
  • Someone should change all the links in here to https:// – RaisingAgent Sep 3 at 12:07

31 Answers 31

The On-Line Encyclopedia of Integer Sequences

  • 1
    repost from last year – Grigory M Feb 1 at 21:29
  • 3
    To quote Brian M. Scott: «This one’s so useful that I even donate a little to them each year» (me too). – Grigory M Feb 1 at 21:30
  • 1
    I've always been a little puzzled by this one's popularity... how often does one need to look up some sequence of integers? Is it actually of practical use or is it mainly for sequence enthusiasts? – rschwieb Feb 8 at 15:36
  • @rschwieb In my case, not terribly often (but then again I don't work very much), but it can be incredibly useful. Just as an example, here is a problem that got a "solution" thanks to OEIS. More generally, I think OEIS makes a nice bridge: lots of discrete things lead to integer sequences. You might work on something, get some numbers, head to OEIS, and find your work is equivalent to some other neat things (which may or may not have been more fully studied). – pjs36 Feb 8 at 17:08
  • 1
    «Pursuing these identities (…) I found that there exists a formula of the same degree of elegance (…) whenever $d$ belongs to the following sequence of integers: $$d=3, 8, 10,14,15, 21, 24, 26, 28, 35, 36,...$$ I stared for a little while at this queer list of numbers (…) they made no sense to me. (…) So I missed the opportunity of discovering a deeper connection between modular forms and Lie algebras.» // Freeman J. Dyson, Missed opportunities, Bull. AMS 78 (1972) – Grigory M Feb 8 at 21:53
  • 1
    @rschwieb Integer sequences are everywhere — from simple combinatorial and number theory problems to coefficients of various power series to dimensions of various objects (irreducible representations of algebras, homotopy groups of spaces, various homology groups…). OEIS helps one to guess answers (and it's usually much easier to solve a problem once you know the answer) and (sometimes) to discover some unexpected connections. Yes, in some situations it's very useful. – Grigory M Feb 8 at 22:09
  • 1
    @GrigoryM Before commenting, I thought it was much as you described, it’s just that I couldn’t believe it would happen frequently enough to count as “incredibly useful”. Maybe once a year at most? In the whole time I’ve thought about research, only one sequence presented itself to me. I guess all it takes is one beautiful connection, though, for the tool to prove itself. – rschwieb Feb 8 at 23:04
  • 3
    @rschwieb Well, yes, it obviously depends on what kind of mathematics you're doing (and in what style). I like enumerative & algebraic combinatorics — where OEIS is quite helpful (and from time to time I see questions on Math.SE where OEIS could have been of help to OP…) – Grigory M Feb 10 at 14:39

Detexify: automated LaTeX symbol recognition


YouTube channel of 3blue1brown

Sage Mathematical Software Environment

ProofWiki, the online compendium of mathematical proofs the leading open access eprint repository

Overleaf: Free online collaborative LaTeX editor with real-time PDF preview


  • 3
    Oh my gosh yes, I don't think this tool gets enough credit. It's simple yet surprisingly powerful. – NetherGranite Mar 23 at 19:22

Wolfram Alpha

Inverse Symbolic Calculator

GAP - Group, Algorithms and Programming

Wolfram Math World

Groupprops, The Group Properties Wiki

NIST Digital Library of Mathematical Functions

  • It is difficult to read "you need" over the dark red on the right side, especially when the image is smaller – Karl May 10 at 18:30
  • @Karl: Then don't read it. The sentence makes sense either way. :-) – Lucian May 11 at 0:41

CoCalc – Collaborative Calculation in the Cloud

Follow us on Twitter!

  • This is a demonstration post to indicate how this should look when an ad is posted. It also doubles as your twitter ad, but it's up to you if you wish to promote it by voting – Grace Note Jan 29 at 5:13

The Combinatorial Statistic Finder

Wolfram Functions

Open network of research problems in mathematics

enter image description here

Join Computer Science Educators Stack Exchange!

Prove theorems to mathdialog and it will interactively teach them!

  • 6
    Shouldn't there be some description in the picture? I had to hover my mouse over it and decipher the url to see that what it was. I have given a course on Maxima, but I didn't recognize the logo... – Joonas Ilmavirta Feb 11 at 14:33

Writing.SE welcomes questions about academic, scientific, and technical writing

Tagline to show on mouseover

Tagline to show on mouseover

  • This is a work with my friend. Apparently we are not big companies like the above. – Zaid Alyafeai Feb 4 at 13:01

Math Playground. Give your brain a workout!

  • 2
    There are size requirements for the images, and I do not think this meets them, unfortunately. – pjs36 Feb 2 at 23:17
  • @pjs36 I don't know a way to fix it. Should I delete my answer? – polfosol Feb 3 at 8:31
  • 1
    @pjs36: Size problem fixed ! – Lucian Feb 8 at 1:40
  • 1
    @polfosol: It's fixed now, so, if size requirements were its only problem, this answer should garner a positive score by the first of March. – Lucian Feb 8 at 2:10

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