Bell Numbers
Generate Bell numbers.
bell(n)
n |
integer, asking for the n-th Bell number. |
Bell numbers, commonly denoted as B_n, are defined as the number of
partitions of a set of n elements. They can easily be calculated
recursively.
Bell numbers also appear as moments of probability distributions, for example
B_n is the n-th momentum of the Poisson distribution with mean 1.
A single integer, as long as n<=22.
sapply(0:10, bell) # 1 1 2 5 15 52 203 877 4140 21147 115975
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