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Concrete mathematics : a foundation for computer science

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196 BINOMIAL COEFFICIENTS<br />

This observation is easy to prove, since those table entries are the h(n,n-2)‘s<br />

and we have<br />

h(n,n-2) = (3 = (3,<br />

It also seems that the numbers in the first two columns differ by fl. Is<br />

this always true? Yes,<br />

h(n,O)-h(n,l) = ni-n(n-l)i<br />

= n!(-‘)” = (-l)n<br />

n!<br />

n(n-l)! t e)<br />

O

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