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%I #39 Jan 31 2023 14:53:37
%S 0,1,2,7,35,228,2237,31559,1668997
%N Number of nonisomorphic monoids (semigroups with identity) of order n.
%H Remigiusz Durka and Kamil Grela, <a href="https://arxiv.org/abs/1911.12814">On the number of possible resonant algebras</a>, arXiv:1911.12814 [hep-th], 2019.
%H Najwa Ghannoum, <a href="https://theses.hal.science/tel-03948327">Investigation of finite categories</a>, Doctoral thesis, Univ. Côte d'Azur (France); Univ. Libanaise (Lebanon), tel-0394832 [math.CT], 2022.
%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 Clayton Cristiano Silva, <a href="http://www.ime.unicamp.br/~ftorres/ENSINO/MONOGRAFIAS/Clayton.pdf">Irreducible Numerical Semigroups</a>, University of Campinas, São Paulo, Brazil (2019).
%H <a href="/index/Mo#monoids">Index entries for sequences related to monoids</a>
%F a(n) = 2*A058133(n) - A058132(n).
%F a(n) < A027851(n) except for equality iff n = 1. - _M. F. Hasler_, Dec 10 2018
%Y Cf. A058132, A058133.
%Y Cf. A027851 (number of all nonisomorphic semigroups).
%K nonn,hard,more
%O 0,3
%A _Christian G. Bower_, Nov 13 2000
%E a(8) from _Christian G. Bower_, Dec 26 2006
%E a(0) = 0 prepended by _M. F. Hasler_, Dec 10 2018
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