6
votes
2answers
132 views

Relatively prime property verification

I am reading a computer science puzzles book. And I get the following question - "You have a five quart jug, a three quart jug and unlimited supply of water. How would you come up with exactly four ...
0
votes
3answers
139 views

A riddle - is there a way to solve it non-numerically?

So the riddle is: John has written down $k$ sequential odd numbers: $n_1, n_2, ..., n_{k-1}, n_{k}$ (where $n_{2} = n_{1} + 2$ and so on). We know that: The sum of the first four numbers is a ...
3
votes
2answers
149 views

Efficiently identifying spam honeypots

I realise that the title is computing specific, but I think the underlying problem is general - I just don't know how to phrase it more generally (which may be part of my problem). So I am asking ...
0
votes
3answers
206 views

Find 7 digit prime numbers with this property;

When you subtract the sum of the squares of the digits of the number from the original number it gives you another prime number squared.
7
votes
1answer
192 views

Flirtatious Primes

Here's a possibly interesting prime puzzle. Call a prime $p$ flirtatious if the sum of its digits is also prime. Are there finitely many flirtatious primes, or infinitely many?
1
vote
1answer
180 views

How to express $2012$ in terms of three consecutive primes?

How to express $2012$ in terms of three consecutive primes if you can use each prime number only once ? Source of this problem you can find on this page . Closest number to the $2012$ ...
6
votes
1answer
151 views

Puzzle: Can you find an elementary proof that every $n \gt 6$ can be represented as a sum of $O(\log n)$ distinct primes?

Can you find an elementary proof that every $n \gt 6$ can be represented as a sum of $O(\log n)$ distinct primes? For example, $11 = 11$, $12 = 5 + 7$, $13 = 2 + 11$, $14 = 2 + 5 + 7$. On the other ...
-1
votes
3answers
564 views

Prime number rule

I was requesting somebody to help me discuss how the prime number rule helps to solve easily the sudoku game in just a few minutes and an example showing the relevant steps on how the rule is used