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%I #10 Jan 11 2013 16:22:16
%S 1,4,81,16384,48828125,2821109907456,3909821048582988049,
%T 154742504910672534362390528,202755595904452569706561330872953769,
%U 10000000000000000000000000000000000000000000000
%N Number of n-element labeled commutative groupoids with an identity.
%C Also labeled commutative groupoids with an absorbant (zero) element.
%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/Groupoid.html">Groupoid.</a>
%H <a href="/index/Gre#groupoids">Index entries for sequences related to groupoids</a>
%F a(n) = n^(1+binomial(n, 2))
%Y a(n) = A076113(n)*n. Cf. A038017.
%K nonn
%O 1,2
%A _Christian G. Bower_, Dec 05 2003