Script to generate a Pascal's Triangle.

pascals_triangle.rb

def pascalsTriangle(n = 1)
  return nil if n == nil || n < 1
  rows = [[1]]
  2.upto(n) do |i|
    row = [1]
    1.upto(i-2) do |j|
      row << rows.last[(j-1) % rows.last.size] + rows.last[j % rows.last.size]
    end
    rows << (row << 1)
  end
  rows.flatten
end