If the difficulty level seems high for you, you will surely want to visit my Parallel Universe 'Probability in My Garden' page. Arriving in the near future, this parallel universe has the same problems on an easier level.
Sequences are so important.
The sequence is 3. The sequence is 11. The sequence is 23 or 32. This is one sequence because we don't care about the order. The sequences are 23 and 32.