Math Is Fun Forum

Hi;

I got the same answer as Bobby's, also with M.

There are 236 solutions to "all values of x such that x^2 + 27 and x + 3 are prime".

No, b$ isn't empty: it contains 21 blank spaces.

Each of the seven lines of printing in your first post contains two equal groups of asterisks that are separated by a group of blank spaces. Line 1 has 3 blank spaces, increasing by 3 in each subsequent line until reaching 21 blank spaces in the last (7th) line.

EDIT: The following code explanation is for the first program in my previous post.

RIGHT$(b$,d*3) for line 1 selects the right-most 3 blank spaces from b$, and, using the increasing value of d, for each subsequent loop selects 3 more spaces from b$ than for the previous line.

RIGHT$(a$,c) for line 1 selects the right-most 7 asterisks from a$, and, using the reducing value of c, for each subsequent loop selects 1 less asterisk from a$ than for the previous line.

Hi;

The grid has six of each of the letters 'S', 'I' and 'X' (not necessarily in order), from which the word 'SIX' can be formed six times.

If 'SIX' represents the number 6, then the sum of the value of the six of them and the seven occurrences of the number 6 is 78 (same as Monox D. I-Fly's answer in post #2).

This uses all grid entries.

Hi;

Here are the results from my PC, running on 64-bit Windows 10 Home with 24GB RAM, and M version 10.2.0.0.

Bobby's:
n=2000: {49.917894397904675, 14.369627144092833}

zetafunc's:
n=2000: {154.0926965884645, 14.369627144092856}
n=1750: {117.00484180506999, 14.362679551713114}

All without Monitor. With Monitor added 3% or so to the time.

Thanks...I'll have a read and report back. Most of today is planned for other things, so I won't be able to get into this right away.

But brekkie first...!

I was just in the middle of changing my post to say it might be something like that.

The Excel add-in that I used to find the 24 solutions to patchy1's 7x7 puzzle is an analytic solver.

Hi Bobby;

Thanks for the matrix info...I think I might be getting it.

I got enzotib's code to work for me, except that I could only get it to give me one answer per evaluation. A subsequent evaluation (or more) gave another answer. Only two answers were ever found, and they were the same as ours.

I couldn't work out how to change the code to output both answers in the one run.

Also, my run time varies from zero to about 100 seconds because of the RandomInteger just after the While.

I can't see how we could use this code on a 7x7 grid like patchy1's puzzle, given the HUGE leap in the number of permutations from my 5x5 puzzle that solves nowhere near fast enough to even think of trying it...unless I can find my time machine.

Hi Bobby;

Excellent! They're the two answers I got, too.

One is just a flip over the S-W/N-E diagonal of the other. I hadn't noticed that before I found my second solution (the non-Solver one), otherwise I could have saved myself a fair bit of extra effort!

There don't seem to be any other solutions.

Could you give me an idea of how to do this in M?

I notice from your answers that you seem to have spotted that the four shaded squares can be treated as white squares for part of the coding. That's how I drew up my Excel Solver model, which helped simplify and shorten the code.

Hi;

For anyone coming across this thread before the puzzle's second appearance here (where it is discussed further), I gave a solution (not sure if it's 'the' solution) in post #13 of that second thread.

I couldn't have destroyed that dream had not that word already been coined. You were bound to find out sooner or later...I'm just sorry it was through me!

In a totally tongue-in-cheek sense, zombies being fictional. As with 'photoshopped', you were bound to find out sooner or later; and so, if I've shattered another dream, I'm sorry it was through me...again!

Off to bed. I'll probably dream about zombies.

Hi Bobby;

Getting in the mood early for Halloween?

Changing the subject...that picture of you in post #28 must have been taken quite some time before your avatar photo!!

The resemblance is still there, though - the distinctive, flared-out ears, the prominent mouth, the piercing gaze, the calm, unruffled look...

But that magnificent Rapunzel ponytail's gone, and the hat would be much more useful now than it was back then!