gavinksong

I agree with karthickgururaj, nice puzzle. (And, thanks to bonanova's puzzle, too.) DejMar, your proof is incorrect for the same reason the answer to plasmid's question above is no. The result is correct however. Congratulations to plasmid for finding the solution! I'm glad you didn't give up. Here's the explanation from BWOC:

I'm actually not quite sure what you mean, but I don't think that's the answer I had in mind.

Whoops. Sorry plainglazed.

Congratulations! The answer I had in mind was sort of a mix between these two answers, but both of yours are valid as well.

How many primes are the between 9 and 100 such that reversing the digits yields another prime? This by itself is way too easy, so try to answer this using as little brute force as possible (or try to lower the upper bound as much as possible).

Credit goes to all contributors for the solutions (including DejMar and plasmid). Thank you, PerhapsCheckItAgain, for this slick puzzle.

One of the answers above came from Dejmar. Another came from Perhaps. I'd rather not involve myself in this argument, but I do think Dejmar shouldn't have gotten so defensive. The best thing he could have done would have been to drop his case after he was told the correct intention of the OP. That said, I also think PerhapsCheckItAgain could have been less harsh about it. After all, we're all friends here. One of the things I like about Brainden is the positive manner of many of the regular members. Let's keep Brainden a pleasant place to be on the Internet.

This is incorrect. DejMar,

The tactic that k-man suggested in his last post is correct. He seemed to have very little faith in it, but carrying it out should reveal the solution.

This is true for all m and n > 1?

But that can't be right. It's too simple. I'm probably missing something...?

Are all the executions on different days?

Finite.

It seems that you've made a small mistake.

How is that possible? o.O

Ok, I'll bite.

Good work, but use spoilers.

Good job. I guess bonanova's first thought was right.

However you want to phrase it. The problem states that you can take as much time and allocate as much memory as you need. I think you will find that it is hard enough just to find something that works.

(Hello, friends. This is yet another puzzle from BWOC. I don't know the solution to this one yet, so I was thinking we could work on this together.) You are tasked with designing a robot to explore a large but finite maze. The maze is drawn on a square grid, and walls exist on some of the edges of the square grid. Some of the squares contain a flag. Your robot may interact with the world in the following ways: 1) Check which of the 4 adjacent edges contain walls. 2) Move to one of the 4 adjacent squares (provided there is no wall in the way). 3) Check if there is a flag on your square. 4) Pick up a flag (provided there is a flag on your square and the robot is not already holding a flag). 5) Put down a flag (provided the robot is holding a flag and there is not already a flag on your square). 6) Generate a random bit. 7) Output a number. Your robot will be placed in a maze. The maze will contain some number of flags (from 100 to 1000). All flags will be reachable from the robot’s starting position. Your robot is tasked with determining the number of flags. The robot may take as long as it needs, but may only output one number and must output the correct answer eventually, with probability 1. The catch is that your robot is not Turing complete. It only has a finite amount of memory. You can give your robot as much memory as you need, but it must succeed on arbitrarily large mazes

Here it is: https://en.m.wikipedia.org/wiki/Erdős–Szekeres_theorem Surprisingly, I think this might hold the key to this question.

This problem reminds me of another unsolvable BMAD puzzle involving the task of sorting DVDs using insertion sort. I think back then, Yoruichi-San, pointed us to a Wikipedia article that showed how to calculate an upper bound.