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 A118127 #6 Mar 30 2012 18:40:36 %S A118127 1,2,3,8,43,1454,1131985,12199587820,2697830531268481, %T A118127 15224736759268778589978,2750892227033887206264514123491 %N A118127 Number of quasigroups of order <= n. %C A118127 A quasigroup is a groupoid G such that for all a and b in G, there exist unique c and d in G such that ac = b and da = b. Hence a quasigroup is not required to have an identity element, nor be associative. Equivalently, one can state that quasigroups are precisely groupoids whose multiplication tables are Latin squares (possibly empty). %H A118127 <a href="/index/Qua#quasigroups">Index entries for sequences related to quasigroups</a>. %F A118127 a(n) = SUM[i=0..n] A057991(i). %e A118127 a(10) = 2750892227033887206264514123491 = 1 + 1 + 1 + 5 + 35 + 1411 + 1130531 + 12198455835 + 2697818331680661 + 15224734061438247321497 + 2750892211809150446995735533513. %Y A118127 Cf. A002860, A057991-A057994, A057771, A057996, A118641. %K A118127 nonn %O A118127 1,2 %A A118127 _Jonathan Vos Post_, May 12 2006