A090604 -id:A090604 - cp's OEIS frontend

A090600 Number of n-element groupoids with an identity, considered to be equivalent when they are isomorphic or anti-isomorphic (by reversal of the operator).

1, 2, 30, 22456, 3179460875, 118459556737869096, 1841479754519556293280702095, 17699004125822025124951660289473617122688, 146207646053305863964379580591072585873215024249550168360

Offset: 1

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Christian G. Bower, Dec 05 2003

nonn

Also partial groupoids with n-1 elements or groupoids with an absorbant (zero) element with n elements in each case the same equivalence.

Eric Postpischil Posting to sci.math newsgroup, May 21 1990
Eric Weisstein's World of Mathematics, Groupoid.
Index entries for sequences related to groupoids

a(n) = (A090601(n) + A090604(n))/2

cp's OEIS Frontend

A090600 Number of n-element groupoids with an identity, considered to be equivalent when they are isomorphic or anti-isomorphic (by reversal of the operator).

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