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Search: id:A108801
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| A108801 |
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Number of nonisomorphic systems enumerated by A102897; that is, the number of inequivalent Horn functions, under permutation of variables. |
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8
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OFFSET
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0,1
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COMMENT
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When speaking of inequivalent Boolean functions, three groups of symmetries are typically considered: Complementations only, the Abelian group (2,...,2) of 2^n elements; permutations only, the symmetric group of n! elements; or both complementations and permutations, the octahedral group of 2^n n! elements. In this case only symmetry with respect to the symmetric group is appropriate because complementation affects the property of being a Horn function..
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REFERENCES
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D. E. Knuth, The Art of Computer Programming, Vol. 4, Section 7.1.1 (in preparation).
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LINKS
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D. E. Knuth, HORN-COUNT
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CROSSREFS
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Equals 2*A108799(n).
Cf. A102894, A102895, A102896, A102897, A108798, A108799, A108800.
Sequence in context: A047142 A081080 A109460 this_sequence A111022 A086852 A084737
Adjacent sequences: A108798 A108799 A108800 this_sequence A108802 A108803 A108804
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KEYWORD
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nonn,hard
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AUTHOR
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D. E. Knuth, Jul 01, 2005; a(6) received Aug 17, 2005
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