I'm trying to give combinatorial (not algebraic!) proofs of the following statements:
(1)
(2)
wheredenotes the number of
-permutations of elements from an
-element set. In other words, if we have an
-element set
then one
-permutation would be an ordered
-tuple of different elements from
, i.e.
such that
whenever
.
Any help would be greatly appreciated!


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