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Re: the number of equivalence relations on {1,2, ...,n}
Posted:
Nov 9, 2012 3:54 AM


On 09/11/2012 06:09, quasi wrote: > For n in N, let e(n) be the number of equivalence relations on > the set {1,2,...,n}
Bell numbers: http://en.wikipedia.org/wiki/Bell_number
> For n,k in N with k <= n, let f(n,k) be the number of equivalence > relations on the set {1,2,...,n} with exactly k equivalence > classes.
Stirling numbers: http://en.wikipedia.org/wiki/Stirling_numbers_of_the_second_kind



