Lah Numbers
Lah Numbers
The Lah numbers count the number of ways to partition a list of elements into disjoint, nonempty subsets, where the order of elements in a subset is significant. This is in contrast to the Stirling numbers of the second kind, which count such partitions where the order of elements in a subset does not matter, and Stirling numbers of the first kind, which consider the cycles of a permutation. This Demonstration illustrates the different partitions that Lah numbers count.
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