[seqfan] (no subject)

[Leroy Quet]

Way to go, Rob! Did you use a computer or find this solution completely by hand?

I wonder how many 18-distinct-products solutions there are. (There are at least 16, with rotations and reflections and flipping all the bits. But besides those solutions, I wonder how hard it is to come across an arrangement of 0's and 1's that work.)

Thanks,
Leroy Quet


[ ( [ ([( [ ( ([[o0Oo0Ooo0Oo(0)oO0ooO0oO0o]]) ) ] )]) ] ) ]


--- On Fri, 6/11/10, Rob Pratt <Rob.Pratt at sas.com> wrote:

> From: Rob Pratt <Rob.Pratt at sas.com>
> Subject: [seqfan] Re: Unique Products Regarding Binary Matrices
> To: "Sequence Fanatics Discussion list" <seqfan at list.seqfan.eu>
> Date: Friday, June 11, 2010, 6:34 PM
> 18:
> 
> 0    0    0    0   
> 0    1    1    1   
> 1
> 0    0    1    0   
> 0    0    0    0   
> 1
> 0    0    0    0   
> 0    0    0    1   
> 1
> 0    1    0    1   
> 0    1    1    1   
> 0
> 0    1    0    1   
> 0    1    0    1   
> 0
> 1    1    0    1   
> 0    1    1    1   
> 0
> 0    0    0    1   
> 1    1    0    1   
> 0
> 0    0    0    0   
> 1    0    1    0   
> 1
> 0    0    0    0   
> 1    0    0    1   
> 0
> 
> Note that for n = 9, there are exactly 18 possible products
> (the ones you list below, and 1), so each one must be used.
> 
> Rob
> 
> -----Original Message-----
> From: seqfan-bounces at list.seqfan.eu
> [mailto:seqfan-bounces at list.seqfan.eu]
> On Behalf Of Douglas McNeil
> Sent: Friday, June 11, 2010 11:57 AM
> To: Sequence Fanatics Discussion list
> Subject: [seqfan] Re: Unique Products Regarding Binary
> Matrices
> 
> > I too have been able to get 16 unique products. But
> getting those last 2 products to differ is a *little*
> tricky, perhaps, if possible.
> 
> I can get 17 -- set([2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14,
> 15, 16, 18,
> 20, 24, 27]) -- but not 18 yet.
> 
> 
> Doug
> 
> --
> Department of Earth Sciences
> University of Hong Kong
> 
> 
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