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by Bob Showalter

(Taken from the puzzle by William Wu at
http://www.ocf.berkeley.edu/~wwu/riddles/cs.shtml)

[Editor's Note:  This was also a code golf problem a few months back: 
http://codegolf.com/oblongular-number-spirals  --JEG2]

Write a Ruby program to print out a "spiral" of numbers that fill a NxN square.
Your program will take a single argument to specify the dimensions of the square
(1 or higher). The number zero represents the center of the spiral, and the
succeeding integers spiral out in a clockwise (or counterclockwise; your choice)
direction from the center until the square is filled.

Your program should write the output line by line, without using an array to
build up the data first.

Here's the output for an 8x8 spiral:

	56   57   58   59   60   61   62   63
	
	55   30   31   32   33   34   35   36
	
	54   29   12   13   14   15   16   37
	
	53   28   11    2    3    4   17   38
	
	52   27   10    1    0    5   18   39
	
	51   26    9    8    7    6   19   40
	
	50   25   24   23   22   21   20   41
	
	49   48   47   46   45   44   43   42