Prime X-Sums
(Published on 27. August 2023, 15:34 by Florian Wortmann)
Normal sudoku rules apply.
X-Sums
A clue outside the grid is the sum of the first X cells in the corresponding row/column, where X is the digit in the cell nearest to the clue.
Just as for the given sums, the sum for a ?-clue is prime, but must be determined by the solver.
Link:
CTC-App
Solution code: row 3
Comments
on 30. August 2023, 07:16 by cmb
nice flow.
on 29. August 2023, 01:10 by nseydel
If we were to accept 1 as a prime (divided only by 1 and itself), prime factorisation would be not unique (e.g. 12 = 2^2 * 3 or 1 * 2^2 * 3 or 1^2 * 2^2 * 3 ...). That would be terrible for any mathematical proof. Primes are the units of numbers, any integer can uniquely be shown as a product of primes (only except for the order of factors). So amongst mathematicians, 1 is NEVER regarded a prime. Remember: a prime is a number with exactly two divisors, but 1 has only a single divisor: 1. That being said, it can never hurt to mention '1 is not a prime' in the rules of a puzzle featuring primes.
on 28. August 2023, 13:42 by Florian Wortmann
formatting
on 28. August 2023, 13:33 by Florian Wortmann
added image of prime numbers
on 28. August 2023, 01:35 by Snaques
It's definitely a 'me' problem, but it might be a nice hint to remind that 1 is not actually a prime number.
I've heard it debated both ways and at least I couldn't find a solution until I confirmed that it is indeed not a prime.
Otherwise very enjoyable puzzle.
--
Thank you for the kind comment. I was not aware that it might be unclear whether 1 is prime or not.
The definition I know is that a number is prime when it has exactly two "real divisors" (not sure if that is the proper english term).
I now added an image with all prime numbers 1-50 to avoid any further confusion.
Snaques: Been a while since I was at school, so I thought a number is a prime if it is only divisible by 1 and the number itself. Internet seems to agree with you, so I just needed a refresher.;)
