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 A079198 #17 Feb 06 2021 15:20:40 %S A079198 0,2,50,2352,153002,15876046,7676692858 %N A079198 Number of associative non-commutative closed binary operations on a set of order n. %C A079198 a(n) + A079192(n) + A079195(n) + A023815(n) = A002489(n). %C A079198 Each a(n) is equal to the sum of the products of each element in row n of A079200 and the corresponding element of A079210. %C A079198 Since this is the number of labeled noncommutative semigroups on an n-set, a(n) = A023814(n)-A023815(n). - _Stanislav Sykora_, Apr 03 2016 %H A079198 C. van den Bosch, <a href="http://cosmos.ucc.ie/~cjvdb1/html/binops.shtml">Closed binary operations on small sets</a> %H A079198 <a href="/index/Se#semigroups">Index entries for sequences related to semigroups</a> %Y A079198 Cf. A023814, A023815, A079192, A079195, A079199, A079200. %K A079198 nonn,more %O A079198 1,2 %A A079198 Christian van den Bosch (cjb(AT)cjb.ie), Jan 03 2003 %E A079198 a(5)-a(7) added by _Stanislav Sykora_, Apr 03 2016