<image>As shown in the diagram, it is a sequence of patterns made up of squares using a certain number of matchsticks. 

(1) Complete the table below:
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(2) A student arranges the patterns using a certain number of matchsticks in the way shown in the diagram. After completing the 1st pattern, then the 2nd, and then the 3rd, 4th, ..., when he finishes the nth pattern, there are 20 matchsticks left. To just complete the (n+1)th pattern, he still needs 2 more matchsticks. Which pattern is the last one he arranged?