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Search: id:A072447
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| A072447 |
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Number of subsets S of the power set P{1,2,...,n} such that: {1}, {2},..., {n} are all elements of S; {1,2,...n} is an element of S; if X and Y are elements of S and X and Y have a non-empty intersection, then the union of X and Y is an element of S. |
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4
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