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Search: id:A128934
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| A128934 |
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Number of centrist groupoids with n elements. |
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+0
1
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OFFSET
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1,4
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COMMENT
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Systems with a binary operation that satisfies AB.BA=B. The rule is anti-commutative. Any central groupoid is centrist.
For comparison, a central groupoid is a system with a binary operator that satisfies the equation AB.BC=B (or (AB)(BC)=B). These have the curious property that the finite systems have a square number of elements. What is the beginning of the sequence giving the number of central groupoids of order n^2?
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CROSSREFS
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Adjacent sequences: A128931 A128932 A128933 this_sequence A128935 A128936 A128937
Sequence in context: A035724 A017721 A042625 this_sequence A116103 A116115 A104380
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KEYWORD
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nonn,more
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AUTHOR
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njas, Apr 28 2007, based on email from Richard Schroeppel (rcs(AT)CS.Arizona.EDU), Mar 15 2007.
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