

A270858


Number of n X n checkered tori (see A179043) with at least one 0 and at least one 1 in each row and each column.


0




OFFSET

1,3


COMMENTS

Let us denote by Qn the set of all n X n binary matrices with at least one 0 and at least one 1 in each row and each column. Let A,B belong to Qn. We will say that A and B are equivalent if B is obtained from A as a result of a sequential cyclic move of the last row or column at a first position. [Please rewrite that sentence!] It's easy to see that this defines an equivalence relation. The sequence gives the number of equivalence classes. The elements of the factorset Qn/~ are relevant in the textile industry.


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KEYWORD

nonn,more


AUTHOR



STATUS

approved



