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Triangle: T(n,k), k<=n: commutative groupoids with a nontrivial symmetry with n elements and k idempotents.
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%I #10 Dec 19 2015 09:51:15

%S 0,0,0,0,0,0,3,6,0,4,96,214,128,64,38,54248,83925,54223,28254,10223,

%T 1894

%N Triangle: T(n,k), k<=n: commutative groupoids with a nontrivial symmetry with n elements and k idempotents.

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

%F Difference of A038021 and A038022.

%Y Cf. A001329, A001425, A030259, A030262, A030265.

%K nonn,tabl,more

%O 0,7

%A _Christian G. Bower_, May 15 1998