I have tried hard to search for this and I'm starting to think I am imagining that it exists. I may have come across this in an old XKCD comic. Imagine crumpling up a number line on a 2d plane. The goal of this format is to keep numbers that are close in value to be close in proximity to each other. I know my example is not going to be perfect, since I don't know the name or exactly how it is done. Any help would be appreciated.
Examples of wrong formats: If you chose the range of 4-6, to group these together you would have to wrap to the new line
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16
This spiral seems a little better, but if you wanted to choose 2-9, it would be a donut shape around the 1.
13 14 15 16
12 3 4 5
11 2 1 6
10 9 8 7
The format I am looking for would probably end up more like this for the numbers 1-16. I kind of remember it snaking back and forth while kind of spiraling out from the middle.
7 6 1 2
8 5 4 3
9 10 11 12
16 15 14 13
It's a variant of the Hilbert R-tree, which is related to the Hilbert curve.