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Number of isomorphism classes of non-associative commutative closed binary operations on a set of order n.
15

%I #11 Jan 26 2022 23:09:11

%S 0,0,1,117,43910,254429575,30468670168769,91267244789189717968,

%T 8048575431238519331999349995,24051927835861852500932966021639447717,

%U 2755731922430783367615449408031031255128360423993

%N Number of isomorphism classes of non-associative commutative closed binary operations on a set of order n.

%H C. van den Bosch, <a href="https://web.archive.org/web/20071014230143/http://cosmos.ucc.ie/~cjvdb1/html/binops.shtml">Closed binary operations on small sets</a>

%H <a href="/index/Gre#groupoids">Index entries for sequences related to groupoids</a>

%F A079193(n) + a(n) + A079199(n) + A001426(n) = A001329(n).

%F a(n) = A001425(n) - A001426(n). - _Andrew Howroyd_, Jan 26 2022

%Y Row sums of A079197.

%Y Cf. A001329, A001425, A001426, A079193, A079195 (labeled case), A079199.

%K nonn

%O 0,4

%A Christian van den Bosch (cjb(AT)cjb.ie), Jan 03 2003

%E a(0)=0 prepended and a(5)-a(10) added by _Andrew Howroyd_, Jan 26 2022