05/28/2008
(n,2) combination
A simple formula in combinatorics: for a combination (n,2) (the number of possible pairs formed by n):
(n,2) = Tn - n
where Tn is the triangle number (eg T5 = 5 + 4 + 3 + 2 + 1 = 15). Proof in file.
(n,2).rtf
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