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Topic: (0,1) Matrices (Read 710 times) 

ThudnBlunder
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(0,1) Matrices
« on: Jan 27^{th}, 2007, 7:37am » 
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Define a (0,1) matrix A as a matrix whose entries are all either 0 or 1. How many nxn (0,1) matrices are there such that A^{2} is also a (0,1) matrix?

« Last Edit: Jan 29^{th}, 2007, 2:10pm by ThudnBlunder » 
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Eigenray
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Re: (0,1) Matrices
« Reply #1 on: Mar 9^{th}, 2007, 9:09am » 
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I haven't done anything more than compute 2, 11, 172, 6327, .... (Do you understand the meaning of 7 X n binary matrices?)


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ThudnBlunder
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Re: (0,1) Matrices
« Reply #2 on: Mar 9^{th}, 2007, 9:39am » 
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on Mar 9^{th}, 2007, 9:09am, Eigenray wrote: No, I don't have an answer for this one.


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Eigenray
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Re: (0,1) Matrices
« Reply #3 on: Mar 9^{th}, 2007, 8:33pm » 
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It's definitely A121231, which may or may not be the same as A122527, but I have no idea how the latter is the "number of 7 X n binary matrices," unless binary matrix means something else there. Presumably balakrishnan knows though.


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