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 A079185 #7 Jul 10 2011 18:42:30 %S A079185 1,0,4,1,4,8,116,0,0,0,8,0,28,504,43428 %N A079185 Number of isomorphism classes of commutative closed binary operations (groupoids) on a set of order n, listed by class size. %C A079185 A079184(n)+A079185(n)=A079171(n). %C A079185 Elements per row: 1,2,4,8,16,30,... (given by A027423, number of positive divisors of n!) %C A079185 First four rows: 1; 0,4; 1,4,8,116; 0,0,0,8,0,28,504,43428 %C A079185 A079176(x) is equal to the sum of the products of each element in row x of this sequence and the corresponding element of A079210. %C A079185 The sum of each row n is given by A079177(n). %H A079185 C. van den Bosch, <a href="http://cosmos.ucc.ie/~cjvdb1/html/binops.shtml">Closed binary operations on small sets</a> %H A079185 <a href="/index/Gre#groupoids">Index entries for sequences related to groupoids</a> %Y A079185 Cf. A001425, A023183, A079184. a(n, A027423(n)) = A030255(n). %K A079185 nonn,tabf %O A079185 1,3 %A A079185 Christian van den Bosch (cjb(AT)cjb.ie), Jan 03 2003