Hi.
This video might help :
When a button is clicked send a event (Button/1 or Button/2 or Button/3)
on the listener fsm have an array with the sequence.
An array starts @ 0 not 1, so index 0 would be 3, index 1 would be 2 and index 2 would be 1 (from your example)
When the event was send (for example Button 3) get the variable ("Array Get" action) @ index 0 (use a variable for the index)
Then compare if the same.
If the same :
Add 1 to the index (and you can do a success sound or something)
Then You can get the 'Array Length' and compare to the index and if equal, then you can do a completed event.
You could also just compare to value 3, but when using 'Array Length' you can easily change to bigger combinations (for example 3,2,3,1,3,1)
If not the same :
Set index Value to 0, send a event to the buttons to reset and optional do a fail sound/animation.