Ordered List

The number of nondecreasing lists {a_1,a_2,...,a_n} consisting of n elements 1<=a_i<=k is given by the binomial coefficient

 N(n,k)=(n+k-1; n-1).

For example, there are six nondecreasing lists of length 2 for elements chosen from 1 to 3: (1, 1), (1, 2), (1, 3), (2, 2), (2, 3), and (3,3).

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Cite this as:

Weisstein, Eric W. "Ordered List." From MathWorld--A Wolfram Web Resource.

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