April 2019

Xyzzy · 2019-04-02, 15:14

http://www.research.ibm.com/haifa/po...April2019.html

bsquared · 2019-04-03, 13:45

Easy to find solutions. I wonder what "elegant" looks like for this puzzle; mine surely are not.

bsquared · 2019-04-03, 14:35

Found a solution for 4x4

a1call · 2019-04-03, 14:50

Quote:

Originally Posted by bsquared

Found a solution for 4x4

I stopped after 21x21. It seems pointless going further up.

bsquared · 2019-04-03, 14:59

Quote:

Originally Posted by a1call

I stopped after 21x21. It seems pointless going further up.

Are all of your averages integers? I.e., all row/col/diag sums are 0 mod 21 as well as prime? If so then you have a much better search algorithm than me.

a1call · 2019-04-03, 15:13

Quote:

Originally Posted by bsquared

Are all of your averages integers? I.e., all row/col/diag sums are 0 mod 21 as well as prime? If so then you have a much better search algorithm than me.

Well shouldn't spoil the challenge at this point but there is a simple algorithm as a factor of number of rows as is obvious with the great number of solutions submitted this early.

lukerichards · 2019-04-03, 16:46

Thanks for sharing. My year 10 class (aged 14-15) had great fun with this today.

petrw1 · 2019-04-03, 17:55

...

a1call · 2019-04-07, 20:36

Well, I did a 101x101 matrix because I found it interesting to write a code to generate a code to solve the large matrix. Otherwise it would have been prohibitively too much work to type the code to check all the 101+101+2 averages.

ETA Again, I wished someone would write a "foreach" style function for the PARI-GP vectors/matrices or add a few decent numeric examples to the forvec loop documentation.

LaurV · 2019-04-08, 15:01

Quote:

Originally Posted by bsquared

all <...> sums are 0 mod 21 as well as prime?

now yafu is very angry with his daddy...

bsquared · 2019-04-09, 13:35

Quote:

Originally Posted by LaurV

now yafu is very angry with his daddy...

Not sure I get it...

Anyway, I picked this back up and figured out a few more things, but I don't think I'll bother to progress much beyond 6x6.

2019-04-02, 15:14	#1
Xyzzy "Mike" Aug 2002 2⁵·257 Posts	April 2019 http://www.research.ibm.com/haifa/po...April2019.html

2019-04-03, 17:55	#8
petrw1 1976 Toyota Corona years forever! "Wayne" Nov 2006 Saskatchewan, Canada 2²·7·167 Posts	Yes quite easy indeed. ...

2019-04-07, 20:36	#9
a1call "Rashid Naimi" Oct 2015 Remote to Here/There 3×5×137 Posts	Well, I did a 101x101 matrix because I found it interesting to write a code to generate a code to solve the large matrix. Otherwise it would have been prohibitively too much work to type the code to check all the 101+101+2 averages. ETA Again, I wished someone would write a "foreach" style function for the PARI-GP vectors/matrices or add a few decent numeric examples to the forvec loop documentation. Last fiddled with by a1call on 2019-04-07 at 20:59

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2019-04-03, 13:45	#2
bsquared "Ben" Feb 2007 3×1,171 Posts	Easy to find solutions. I wonder what "elegant" looks like for this puzzle; mine surely are not.

2019-04-03, 14:35	#3
bsquared "Ben" Feb 2007 3·1,171 Posts	Found a solution for 4x4

2019-04-03, 16:46	#7
lukerichards "Luke Richards" Jan 2018 Birmingham, UK 100100000₂ Posts	Thanks for sharing. My year 10 class (aged 14-15) had great fun with this today.