Monday, September 17, 2007

Catalan numbers

The Catalan Numbers express the number of ways you can divide a polygon with N sides into triangles, using non-intersecting diagonals.



no. of polygon sides      3   4   5   6   7   8    9
no. of ways to divide 1 2 5 14 42 132 429

Euler's formula to generate the Catalan Numbers is
  2 * 6* ..... (4n-10)
_____________________
(n-1)!

an example of catalan in a hexagon is shown in a figure.


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