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A128934 Number of centrist groupoids with n elements. 0

%I

%S 1,0,0,58,6634,0

%N Number of centrist groupoids with n elements.

%C Systems with a binary operation that satisfies AB.BA=B. The rule is anti-commutative. Any central groupoid is centrist.

%C 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?

%K nonn,more

%O 1,4

%A _N. J. A. Sloane_, Apr 28 2007, based on email from Richard C. Schroeppel (rcs(AT)CS.Arizona.EDU), Mar 15 2007.

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Last modified January 16 23:43 EST 2022. Contains 350377 sequences. (Running on oeis4.)