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 A079209 #6 Jul 10 2011 18:22:18 %S A079209 0,0,3,0,0,3,9,0,0,0,3,0,0,16,39 %N A079209 Number of isomorphism classes of associative commutative non-anti-associative non-anti-commutative closed binary operations on a set of order n, listed by class size. %C A079209 A079202(n)+A079203(n)+A079204(n)+A079205(n)+A079197(n)+A079207(n)+A079208(n)+A079209(n)+A063524(n)=A079171(n) %C A079209 Elements per row: 1,2,4,8,16,30,... (given by A027423, number of positive divisors of n!) %C A079209 First four rows: 0; 0,3; 0,0,3,9; 0,0,0,3,0,0,16,39 %C A079209 A079244(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 A079209 The sum of each row x of this sequence is given by A079245(x). %H A079209 C. van den Bosch, <a href="http://cosmos.ucc.ie/~cjvdb1/html/binops.shtml">Closed binary operations on small sets</a> %H A079209 <a href="/index/Se#semigroups">Index entries for sequences related to semigroups</a> %Y A079209 Cf. A079202, A079203, A079204, A079205, A079197, A079207, A079208, A079244, A079245. %K A079209 nonn,tabf %O A079209 1,3 %A A079209 Christian van den Bosch (cjb(AT)cjb.ie), Jan 03 2003