Charlie's Delightful Machine
Hannah from Wallington High School for Girls suggested a possible starting point:
A strategy is to perhaps type in a number one by one so start with 1 then
2,3,4 etc and recording each light that gets turned on.
The Year 9 Puzzle Club at Huddersfield Grammar School worked out their machine's rules as follows:
We wrote down which lights lit up for numbers 1-45, then wrote down the sequences for each colour.
Yellow: 1, 11, 21, 31, 41...
Blue: 11, 22, 33, 44...
Green: 10, 21, 32, 43...
Red: 4, 10, 16, 22, 28...
Then we worked out the Nth term of each sequence.
Yellow: 10N+1
Blue: 11N
Green: 11N-1
Red: 6N-2
Dylan, from Landau Forte, told us his findings:
I found out that yellow started on 3 and I had to add 3 each time. All the numbers were a mixture of odd and even. Next, red started on 7 and I had to add 7 each time. The rule was all the numbers were a mixture of odd and even. Then blue started on 4 and I had to add 9 each time. The rule for this one was also that the numbers were odd and even. Finally green started on 3 and I had to add 4 each
time. The rule for this was that all the numbers were odd.
Laurynne from Wallington pointed out that if the sequence has the rule $an+b$ with $a$ and $b$ both even, the terms will all be even, but if $a$ is even and $b$ is odd, the terms will all be odd.
Aswaath, from Garden International School, tested the machine in the same way, but gave us some extra interesting information about his machine's behaviour:
First, I experimented with the machine, and got these results:
| Green |
Blue |
Red |
Yellow |
| 2 |
10 |
5 |
0 |
| 12 |
22 |
8 |
12 |
| 22 |
34 |
11 |
24 |
| 32 |
46 |
14 |
36 |
| 42 |
58 |
17 |
48 |
| 52 |
70 |
20 |
60 |
| ... |
... |
... |
... |
From this I figured out the nth term of the pattern for each colour:
Green: 10n - 8
Blue: 12n - 2
Red: 3n + 2
Yellow: 12n - 12
From this I figured out all the numbers that made blue, yellow and green light up are even. The numbers for red are a mixture of odd and even as they increase by threes every time.
To take the the investigation further, I also recorded the results for various combinations of colours, in the table below:
| G |
B |
R |
Y |
GY |
GB |
GR |
BY |
BR |
RY |
GYB |
RGY |
| 2 |
10 |
5 |
0 |
12 |
22 |
32 |
- |
- |
- |
- |
- |
| 12 |
22 |
8 |
12 |
72 |
82 |
62 |
|
|
|
|
|
| 22 |
34 |
11 |
24 |
|
|
92 |
|
|
|
|
|
| 32 |
46 |
14 |
36 |
|
|
|
|
|
|
|
|
From this I figured out the nth term of the pattern for the colour combinations:
Green + yellow: 60n - 48
Green + blue: 60n - 38
Green + red: 30n + 2