p-System
A p-system of a set S is a sequence of subsets A_1, A_2, ..., A_p of S, among which some may be empty or coinciding with each other.
See also
Inclusion-Exclusion Principle, k-Subset, SubsetExplore with Wolfram|Alpha
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References
Comtet, L. Advanced Combinatorics: The Art of Finite and Infinite Expansions, rev. enl. ed. Dordrecht, Netherlands: Reidel, pp. 176-177, 1974.Referenced on Wolfram|Alpha
p-SystemCite this as:
Weisstein, Eric W. "p-System." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/p-System.html