Pascal's rulePascalsRule2001-10-16 08:48:252002-11-07 21:23:15Theoremnumber theory combinatorics\usepackage{amssymb}
\usepackage{amsmath}
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\usepackage{xypic}Pascal's rule is the binomial identity
\[ \binom{n}{k} + \binom{n}{k-1} = \binom{n+1}{k} \]
where $1 \leq k \leq n$ and $\binom{n}{k}$ is the binomial coefficient.