How do I come up with a random sequence of unique numbers?

Random(0,5)[/code:rejosrjp]
However, this will generate any random float between 0 and 5, so it allows for things like 0.1, 1.5, 2.3, etc.
to combat this you can add an additional parameter in.
[code:rejosrjp]round(random(0,5))[/code:rejosrjp]
this will round the float up to a whole number.
0.4 becomes 1. 
1.5 becomes 2.
2.3 becomes 3.
If you want to round the number down you can use:
[code:rejosrjp]floor(random(0,5))[/code:rejosrjp]
This will floor the number.
0.4 becomes 0.
1.5 becomes 1.
2.3 becomes 2.
In order to check if there is any repeats, you could store the generated number in a separate variable and then run a check after each number generation to see if it exists, if it does, then re-run the generation code.

As an example, this is how you would set a text box to a random array value.
[img="https://s27.postimg.org/48owzty9f/random.png"]

Hope that helps.