Showing posts with label polyominoes. Show all posts
Showing posts with label polyominoes. Show all posts

Tuesday, 20 February 2024

Digits 3 to 9 in Conway's Game of Life

In my previous post, I looked at the behaviour of the digits 0, 1 and 2 under the rules of Conway's Game of Life. Today I'll look at the digits 3, 4, 5, 6, 7, 8 and 9. Let's start with the digit 3. See Figure 1.


Figure 1: 3 in the shape of an 11-omino

After about 50 steps it ends up in the form shown in Figure 2. There are two ships, two blocks, two beehives and one blinker.


Figure 2: three types of still life and one blinker

Now let's look at the digit 4 shown in Figure 3. It completely disappears after 12 steps or generations, so there's no final state that needs to shown.


Figure 3: the digit 4 in the shape of an octomino
It disappears after 12 generations

The digit 5 is shown in Figure 4 and after three steps or generations it changes into the shapes shown in Figure 5. It's really the same shape as the digit 2 and so the outcomes are basically the same, just differently orientated.


Figure 4: the digit 5 in the shape of an 11-omino


Figure 5: final state of 5 produces two boats

The digit 6 shown in Figure 6 has by far the most complicated behaviour of all the digits. After well over a thousand generations it turns into what is shown in Figure 7.


Figure 6: the digit 6 in the shape of a 12-omino


Figure 7: the complicated final state of the digit 6.
There are additional gliders not shown

Figure 8 shows the digit 7 that, after six generations, turns into a blinker.


Figure 8: the digit 7 as an heptomino
After six generations it becomes a blinker

The digit 8, shown in Figure 9, disappears after 21 generations:


Figure 9: the digit 8 as a 13-omino
It disappears after 21 generations

The digit 9, shown in Figure 10, will behave exactly the same way as for the digit 6, only the orientation will be different.


Figure 10: the digit 9 represented as a 12-omino
It behaves the same as the digit 6

Wednesday, 23 June 2021

PolyKnights

 


To quote from Wikipedia:

A polyknight is a plane geometric figure formed by selecting cells in a square lattice that could represent the path of a chess knight in which doubling back is allowed. It is a polyform with square cells which are not necessarily connected, comparable to the polyking. Alternatively, it can be interpreted as a connected subset of the vertices of a knight's graph, a graph formed by connecting pairs of lattice squares that are a knight's move apart.

It would seem that the definition should read "doubling back is not allowed" since none of the examples shown features "doubling back" in the sense of returning to a previously occupied square.

Today I turned 26379 days and this number happens to be a member of OEIS A030446:


 A030446

Number of \(n\)-celled polyknights (polyominoes connected by knight's moves).   

In the comments to this sequence, it is stated that:

A polyknight is a variant of a polyomino in which two tiles a knight's move apart are considered adjacent. A polyknight need not be connected in the sense of a polyomino. These are free polyknights.

By free here is meant that the pieces can be picked up and turned over, as opposed to one-sided pieces that cannot be picked up and flipped over or fixed pieces that cannot be moved at all. Figures 1 and 2 help explain the differences, using tri-knights are examples:

Figure 1

Figure 2

The six possible tri-knights are shown in Figure 3:

Figure 3

Figure 4 shows a table from Wikipedia listing the different numbers of free, one-sided and fixed polyknights:

Figure 4

As can be seen, the sequence for \(n\) polyknights runs: 1, 1, 6, 35, 290, 2680, 26379 and the numbers very large very quickly. However, for one-sided and fixed polyknights, they rise ever more quickly. The shapes when \(n=7\) could be called heptaknights. Figure 5 shows three examples out of the 26379 possibilities for free heptaknights.

Figure 5

It's also apparent from the sequence terms in Figure 4 that I won't encounter any more polyknight days in this lifetime. The next free polyknight number is 267,598, the next one-sided polyknight number is 52,484 and the next fixed polyknight number is 209,608. 

For information on polykings, follow this link: https://mathworld.wolfram.com/Polyplet.html