Ponder This - March 2023

[SmartMersenne]

Originally Posted by uau

Do an exhaustive search of all possible solutions.

What if it is taking forever?

[EdH]

Well, there you have it! The list is out and I'm not on it, so even though I wrote two separate programs which gave the same answer, I apparently don't know what I'm doing. Whether I will try again in the remaining time is undetermined.

[uau]

Originally Posted by EdH

Well, there you have it! The list is out and I'm not on it, so even though I wrote two separate programs which gave the same answer, I apparently don't know what I'm doing.

Note that the list only has solutions up to 2023-03-05 (while having them for every day until then, so not like there would be very few solvers). If you submitted a solution later, it might not show up. Though it is weird that if they post a list of solutions submitted before a particular date, they'd do it so long after that date.

[EdH]

Originally Posted by uau

Note that the list only has solutions up to 2023-03-05 (while having them for every day until then, so not like there would be very few solvers). If you submitted a solution later, it might not show up. Though it is weird that if they post a list of solutions submitted before a particular date, they'd do it so long after that date.

Thanks! This was also pointed out to me elsewhere. Indeed, my solutions were submitted after the last date listed. I need more patience.

[henryzz]

Originally Posted by EdH

Well, there you have it! The list is out and I'm not on it, so even though I wrote two separate programs which gave the same answer, I apparently don't know what I'm doing. Whether I will try again in the remaining time is undetermined.

Are you accounting for the fact that exceptions can have a digit not 1379 as the last digit or just not be prime? The example makes it look like you just need to try the former.

[EdH]

Originally Posted by henryzz

Are you accounting for the fact that exceptions can have a digit not 1379 as the last digit or just not be prime? The example makes it look like you just need to try the former.

I believe I accounted for everything in the base solution, as long as the final result was prime (chained prime). In fact, my solution does contain some even digits. The bonus gave me more complication with my inclusions.

But, I may have been too hasty with my posting here. I was a bit discouraged by the posting and only noticed my omission. Although I saw the last date, it was at a glance and I misread it as May 3 rather than 5 Mar, which which added my misunderstanding.

[uau]

Originally Posted by EdH

as long as the final result was prime

The task description very explicitly says that is not required.

[EdH]

Originally Posted by uau

The task description very explicitly says that is not required.

I beg to differ on that point. There is a difference between a prime chain and a chained prime. Both are mentioned, but the solution needs to be a chained prime. I can't see how a chained prime could be other than a prime. But, then again, my name is not listed.

[chalsall]

Originally Posted by EdH

I beg to differ on that point.

You guys work at levels I couldn't even dream about.

At the same time... One trusts one's friends know what they are doing...

[science_man_88]

What we know:

• Starting with 2,5,or 8 leads to exemptions needed nearly immediately ( because 2,5,8 ending isn't prime beyond a length 1 string, and switching to 1,4,7 leads to divisibility by 3)
• Starting with 1,4,7 either starts out composite or has at most 2 uses before exemptions forced.

[uau]

Originally Posted by EdH

I beg to differ on that point. There is a difference between a prime chain and a chained prime.

First, the description defines "n-exception chained primes" as numbers appearing in a chain with at most n exceptions (so any number in a such a chain satisfies the definition). Then it explicitly confirms that with "Note that p can also be non-prime, if it is considered one of the exceptions.".

Earlier there was also a remark in parentheses something like "so it'd be called a non-prime n-exception chained prime?", making that part even harder to miss, but that extra remark has apparently just been removed.