# Collatz calculator

Grundsätzlich IT B.V. would like to publish a small javascript tool: the Collatz Calculator, on the occasion of the publication of a new proof of the Collatz Conjecture.

Two days ago Peter Schorer published a new proof of the famous mathematical problem named the Collatz Conjecture. This doesn’t mean it has been proven, though: new proofs for this particular problem appear with depressing regularity, only to be invalidated in a few weeks. But we can always hope for the best!

The problem itself can be stated in simple terms:

Take any positive integer n.

• If n is even, divide it by 2 to get n / 2
• If n is odd, multiply it by 3 and add 1 to obtain 3n + 1

Repeat the process (which has been called “Half Or Triple Plus One”, or HOTPO[7]) indefinitely.

The conjecture is that no matter what number you start with, you will always eventually reach 1. This seems easy to prove, but the Collatz mapping above exhibits chaotic, even fractal behaviour. Thus, a proof has long been sought but not yet been found. Due to the relationship to several other longstanding mathematical problems, this problem has occupied mathematicians for at least a century, possibly much longer than that. Leading to frustration in some quarters.

To get some idea of the complexities of the mapping, feel free to play with this Collatz Calculator (javascript): Start the Collatz Calculator

# A jQuery cheat sheet

A few days ago we received an e-mail from Robert Mening at WebsiteSetup.org, who kindly pointed us to his jQuery cheat sheet. There are of course more than a few cheatsheets for jQuery out there, but this one at least has the advantage that it all fits on one page.

Ronald Kunenborg | march 2017.

The cheat sheet can be found at the bottom of this page. Note that clicking on the image will take you to a webpage where you can also find a PDF-version of the cheat sheet. Alternative cheat sheets can of course be found with a quick search on Google, and from various sources that integrate others (for instance at https://www.sitepoint.com/10-jquery-cheat-sheets/ ). The ones we found most useful though, are the following:

We do have some issues with the cheat sheets in question: there is usually no license on the sheet itself, and the version of jQuery for which it is relevant isn’t always mentioned. These small failings also apply to the cheat sheet shown below. However, if you’re doing some jQuery work now and then, you could do worse than just putting up a copy of the cheat sheet displayed here.

Image source: websitesetup.org – free to link with attribution