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 A243931 #32 Nov 03 2014 17:09:09 %S A243931 1,1,2,4,10,31,120,594,4013,35092,428080,6851545,153025576,4535778875, %T A243931 187380634539,10385121165057,801710433900516 %N A243931 Number of isomorphism classes of 2-reductive involutory abelian/medial quandles. %C A243931 Both names "abelian" and "medial" refer to the identity (xy)(uv)=(xu)(yv). A quandle is called 2-reductive if all orbits are projection quandles. A (left) quandle is involutory (aka symmetric, kei) if all (left) translations have order at most 2, i.e., x(xy)=y is satisfied. %H A243931 <a href="/A243931/b243931.txt">Table of n, a(n) for n = 1..17</a> %H A243931 P. Jedlička, A. Pilitowska, D. Stanovský, A. Zamojska-Dzienio, <a href="http://arxiv.org/abs/1409.8396">The structure of medial quandles</a>, arXiv:1409.8396 [math.GR], 2014. %H A243931 David Stanovský, <a href="http://www.karlin.mff.cuni.cz/~stanovsk/quandles/">Calculating with quandles</a> GAP code to calculate the numbers. %Y A243931 Cf. A242044, A242275. %K A243931 nonn,hard %O A243931 1,3 %A A243931 _David Stanovsky_, Oct 01 2014