Pascal's Triangle

Given an input parameter numRows, generate the first numRows number of rows of Pascal's triangle. As a quick refresher - in a Pascal's triangle, each number is equal to the sum of the two directly above it.

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Example:

Input  : 4  
Output : 
        [
             [1],
            [1,1],
           [1,2,1],
          [1,3,3,1]
         
        ]