CSC 15 Programming Challenge: Pascal's Triangle


Write a function in Python to print the first n rows of Pascal's Triangle.
Information on this famous structure can be found at 
en.wikipedia.org/wiki/Pascal's_triangle 

The first five rows of the triangle are:

      1
     1 1
    1 2 1
   1 3 3 1
  1 4 6 4 1

That is, each number is the sum of the two numbers immediately above it.

You are to write a function  pascal(n) that prints the first n rows.  The
output should be properly formated.


Strategic hints:

  Construct an array representing the numbers on each row.  Worry about the
spacing last.


Technical hints:

  To neatly align the numbers you can use "\t" to tab, or use formated output.
For example, if x is an integer value then

print "%4d" % x

will print the value of x using 4 spaces.