April 2019
 

[url]http://www.research.ibm.com/haifa/ponderthis/challenges/April2019.html[/url]

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

Found a solution for 4x4

[QUOTE=bsquared;512541]Found a solution for 4x4[/QUOTE]
I stopped after 21x21. It seems pointless going further up.:smile:

[QUOTE=a1call;512544]I stopped after 21x21. It seems pointless going further up.:smile:[/QUOTE]

:shock:

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.

[QUOTE=bsquared;512545]:shock:

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.[/QUOTE]
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.

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

Yes quite easy indeed.
 

...

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.:smile:

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.

[QUOTE=bsquared;512545]all <...> sums are 0 mod 21 as well as prime?[/QUOTE]
:shock: now yafu is very angry with his daddy... :razz:

[QUOTE=LaurV;513087]:shock: now yafu is very angry with his daddy... :razz:[/QUOTE]

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.