[seqfan] Re: [math-fun] EXACT matrix factorizations
njasloane at gmail.com
Tue May 7 20:37:19 CEST 2013
Edwin, Thanks, I will enter that sequence this afternoon.
I was wrong of course in calling it a ring (the result of too many
years working in the "mod 2" world - and there the same sequence is
also of interest but is probably in the OEIS already:
number of nxn matrices over GF(2) that are squares). It is just a set.
On Tue, May 7, 2013 at 2:17 PM, W. Edwin Clark <wclark at mail.usf.edu> wrote:
> Brute force gives the following for a(n) = number of squares in M(n,2) =
> ring of nxn matrices over GF(2),
> beginning with n = 1:
> which is not in the OEIS. Perhaps some interested soul can extend this.
> On Tue, May 7, 2013 at 1:08 PM, Neil Sloane <njasloane at gmail.com> wrote:
>> That's related to several questions that have interested me for decades.
>> Here's a simple version: choose your favorite matrix ring R,
>> e.g. real matrices with entries that are 0 or 1.
>> What is a(n) := number of nxn matrices in R that have a square root in R?
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