Combinatorics › Sets and Venn diagrams › Counting relations and functions

Partition of a set with size conditions

High school · ●●●○○ 50 pts

Let NN be the number of ordered pairs of nonempty sets A\mathcal{A} and B\mathcal{B} such that A∪B={1,2,3,4,5,6,7,8,9,10,11,12}\mathcal{A} \cup \mathcal{B} = \{1,2,3,4,5,6,7,8,9,10,11,12\}, A∩B=∅\mathcal{A} \cap \mathcal{B} = \emptyset, the number of elements of A\mathcal{A} is not an element of A\mathcal{A}, and the number of elements of B\mathcal{B} is not an element of B\mathcal{B}. Find NN.

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set partitionscountingbinomial coefficientsinclusion-exclusion