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A128934
Number of centrist groupoids with n elements.
0
1, 0, 0, 58, 6634, 0
OFFSET
1,4
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?
CROSSREFS
Sequence in context: A250919 A282438 A308391 * A173955 A243466 A201988
KEYWORD
nonn,more
AUTHOR
N. J. A. Sloane, Apr 28 2007, based on email from Richard C. Schroeppel (rcs(AT)CS.Arizona.EDU), Mar 15 2007.
STATUS
approved