This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A384190 #34 May 26 2025 05:50:12
%S A384190 1,3,20,331,31913,40104513,643460323187
%N A384190 Number of non-isomorphic AG-groupoids of order n.
%C A384190 A magma S is called an Abel-Grassmann or AG-groupoid (historically they were also called left almost semigroups, right modular groupoids and left invertive groupoids) if for all a,b,c in S (ab)c = (cb)a.
%D A384190 M. A. Kazim and M. Naseerudin, On almost semigroups, Alig. Bull. Math. 2, 1-7 (1972).
%H A384190 Marek Dančo, Mikoláš Janota, Michael Codish, and João Jorge Araújo, <a href="https://doi.org/10.48550/arXiv.2502.10155">Complete Symmetry Breaking for Finite Models</a>, arXiv:2502.10155 [cs.LO], 2025.
%H A384190 Marek Dančo, <a href="https://github.com/MarekDanco/symmetrybreaking/">MACE-like model finder for algebraic structures</a>.
%H A384190 Andreas Distler, Muhammad Shah, and Volker Sorge, <a href="https://doi.org/10.1007/978-3-642-22673-1_1">Enumeration of AG-Groupoids</a>, Davenport, J.H., Farmer, W.M., Urban, J., Rabe, F. (eds) Intelligent Computer Mathematics. CICM 2011. Lecture Notes in Computer Science, vol 6824. Springer, Berlin, Heidelberg.
%H A384190 Muhammad Iqbal, Imtiaz Ahmad, Muhammad Shah, and Muhammad Irfan Ali, <a href="https://doi.org/10.48550/arXiv.1510.01316">On cyclic associative Abel-Grassman groupoids</a>, arXiv:1510.01316 [math.GR], 2015.
%H A384190 <a href="/index/Gre#groupoids">Index entries for sequences related to groupoids</a>
%e A384190 For a(2) there are only 3 non-isomorphic AG-groupoids: the null semigroup, the semigroup formed by the set {0,1} under multiplication and the cyclic group Z2.
%Y A384190 Cf. A001329 (magmas), A124506 (semigroups), A001426, A350875, A350874.
%K A384190 nonn,hard,more
%O A384190 1,2
%A A384190 _Elijah Beregovsky_, May 21 2025