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A128934
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Number of centrist groupoids with n elements.
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0
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OFFSET
| 1,4
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COMMENTS
| 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
| Sequence in context: A017721 A207278 A042625 * A201988 A116103 A116115
Adjacent sequences: A128931 A128932 A128933 * A128935 A128936 A128937
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KEYWORD
| nonn,more
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Apr 28 2007, based on email from Richard Schroeppel (rcs(AT)CS.Arizona.EDU), Mar 15 2007.
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