How to Display a Multiplication Table Using Ruby

I needed to display a multiplication table of the first n prime numbers, where n is kept below 10. I chose ruby to solve the problem, because it has an implementation of the Sieve of Eratosthenes, out of the box(!!!). First the code:

And a sample run:

     2    3    5    7    11   13   17   19   23   29
     ---- ---- ---- ---- ---- ---- ---- ---- ---- ----
2  | 4    6    10   14   22   26   34   38   46   58
3  | 6    9    15   21   33   39   51   57   69   87
5  | 10   15   25   35   55   65   85   95   115  145
7  | 14   21   35   49   77   91   119  133  161  203
11 | 22   33   55   77   121  143  187  209  253  319
13 | 26   39   65   91   143  169  221  247  299  377
17 | 34   51   85   119  187  221  289  323  391  493
19 | 38   57   95   133  209  247  323  361  437  551
23 | 46   69   115  161  253  299  391  437  529  667
29 | 58   87   145  203  319  377  493  551  667  841