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%I #29 Jan 14 2024 06:53:39
%S 1,1,8,113,3492,183732,17061118,7743056064,148195347518186,
%T 38447365355811944462
%N Number of associative binary operations on an n-set; number of labeled semigroups.
%H Alex Bailey, Martin Finn-Sell, and Robert Snocken, <a href="http://arxiv.org/abs/1409.2444">Subsemigroup, ideal and congruence growth of free semigroups</a>, arXiv preprint arXiv:1409.2444 [math.GR], 2014.
%H A. Distler and T. Kelsey, <a href="http://arxiv.org/abs/1301.6023">The semigroups of order 9 and their automorphism groups</a>, arXiv preprint arXiv:1301.6023 [math.CO], 2013.
%H C. Noebauer, <a href="http://www.algebra.uni-linz.ac.at/~noebsi/">Home page</a> [broken link]
%H C. Noebauer, <a href="ftp://www.algebra.uni-linz.ac.at/pub/noebauer/smallrings.ps.gz">The Numbers of Small Rings</a>
%H C. Noebauer, <a href="ftp://www.algebra.uni-linz.ac.at/pub/noebauer/thesis.ps.gz">Thesis on the enumeration of near-rings</a>
%H Eric Postpischil <a href="http://groups.google.com/groups?&hl=en&lr=&ie=UTF-8&selm=11802%40shlump.nac.dec.com&rnum=2">Posting to sci.math newsgroup, May 21 1990</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Semigroup.html">Semigroup.</a>
%H <a href="/index/Se#semigroups">Index entries for sequences related to semigroups</a>
%Y Cf. A001423, A001426, A023813, A023815, A027851.
%Y a(n) + A079172(n) = A002489(n).
%K nonn,more
%O 0,3
%A Lyle Ramshaw (ramshaw(AT)pa.dec.com)
%E a(8), a(9) from Distler and Kelsey (2013). - _N. J. A. Sloane_, Feb 19 2013
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