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 A079197 #6 Jul 10 2011 18:42:31 %S A079197 0,0,1,1,4,5,107,0,0,0,5,0,28,488,43389 %N A079197 Number of isomorphism classes of non-associative commutative closed binary operations on a set of order n, listed by class size. %C A079197 A079194(n)+A079197(n)+A079200(n)+A079201(n)=A079171(n). %C A079197 Elements per row: 1,2,4,8,16,30,... (given by A027423, number of positive divisors of n!) %C A079197 First four rows: 0; 0,1; 1,4,5,107; 0,0,0,5,0,28,488,43389 %C A079197 A079195(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 A079197 The sum of each row x of this sequence is given by A079196(x). %H A079197 C. van den Bosch, <a href="http://cosmos.ucc.ie/~cjvdb1/html/binops.shtml">Closed binary operations on small sets</a> %H A079197 <a href="/index/Gre#groupoids">Index entries for sequences related to groupoids</a> %Y A079197 Cf. A079194, A079198, A079199, A079200, A079201. %K A079197 nonn,tabf %O A079197 1,5 %A A079197 Christian van den Bosch (cjb(AT)cjb.ie), Jan 03 2003