Fourteen numbers around a circle
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Place the numbers 1 to 14 around this circle so that both the sum and (absolute) difference of any two neighboring numbers is a prime.
mathematics number-theory
asked 2 hours ago
Bernardo Recamán Santos
2,1881139
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up vote
4
down vote
favorite
Place the numbers 1 to 14 around this circle so that both the sum and (absolute) difference of any two neighboring numbers is a prime.
mathematics number-theory
asked 2 hours ago
Bernardo Recamán Santos
2,1881139
Was this an original question? Or do you have a source?
– Dr Xorile
25 mins ago
add a comment |
up vote
4
down vote
favorite
up vote
4
down vote
favorite
Place the numbers 1 to 14 around this circle so that both the sum and (absolute) difference of any two neighboring numbers is a prime.
mathematics number-theory
asked 2 hours ago
Bernardo Recamán Santos
2,1881139
Place the numbers 1 to 14 around this circle so that both the sum and (absolute) difference of any two neighboring numbers is a prime.
mathematics number-theory
mathematics number-theory
asked 2 hours ago
Bernardo Recamán Santos
2,1881139
asked 2 hours ago
Bernardo Recamán Santos
2,1881139
asked 2 hours ago
Bernardo Recamán Santos
2,1881139
asked 2 hours ago
Bernardo Recamán Santos
2,1881139
asked 2 hours ago
Bernardo Recamán Santos
2,1881139
2,1881139
Was this an original question? Or do you have a source?
– Dr Xorile
25 mins ago
add a comment |
Was this an original question? Or do you have a source?
– Dr Xorile
25 mins ago
Was this an original question? Or do you have a source?
– Dr Xorile
25 mins ago
Was this an original question? Or do you have a source?
– Dr Xorile
25 mins ago
add a comment |
1 Answer
1
active
oldest
votes
up vote
5
down vote
This appears to work, and I think it's unique but haven't checked super-carefully:
10 -- 13 -- 6 -- 11 -- 8 -- 3 -- 14 -- 9 -- 2 -- 5 -- 12 -- 1 -- 4 -- 7 -- (10)
answered 2 hours ago
Gareth McCaughan♦
59.4k3150230
Was about to post this too, and I'm pretty sure it's unique because: there are 2 or 3 possibilities for the neighbours of each number, if 2 then it's forced, and then we can draw a graph for the remaining and there is only one cycle covering all numbers.
– deep thought
2 hours ago
To expand a bit: 2,11,13,14 can each only be adjacent to two numbers, so that part of the sequence is forced, namely 3-14-9-2-5 and 10-13-6-11-8. 1 could neighbour 4,6,12 but 6 is now "taken" by 13 and 11, so 12-1-4 is forced. 4 could neighbour 9 but 9 is also taken, 1-4-7. 12 could neighbour 7 but that would close off a cycle of length 4. So 12 and 7 are forced: 7-10 and 5-12. 3 could neighbour 10 but that's taken. so 8-3. Done.
– deep thought
1 hour ago
Sorry if I ninjaed you! Your reasons for saying it's unique are very much like mine (unsurprisingly) but since I hadn't bothered to write them out carefully I didn't want to claim too much :-).
– Gareth McCaughan♦
1 hour ago
add a comment |
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
5
down vote
This appears to work, and I think it's unique but haven't checked super-carefully:
10 -- 13 -- 6 -- 11 -- 8 -- 3 -- 14 -- 9 -- 2 -- 5 -- 12 -- 1 -- 4 -- 7 -- (10)
answered 2 hours ago
Gareth McCaughan♦
59.4k3150230
Was about to post this too, and I'm pretty sure it's unique because: there are 2 or 3 possibilities for the neighbours of each number, if 2 then it's forced, and then we can draw a graph for the remaining and there is only one cycle covering all numbers.
– deep thought
2 hours ago
To expand a bit: 2,11,13,14 can each only be adjacent to two numbers, so that part of the sequence is forced, namely 3-14-9-2-5 and 10-13-6-11-8. 1 could neighbour 4,6,12 but 6 is now "taken" by 13 and 11, so 12-1-4 is forced. 4 could neighbour 9 but 9 is also taken, 1-4-7. 12 could neighbour 7 but that would close off a cycle of length 4. So 12 and 7 are forced: 7-10 and 5-12. 3 could neighbour 10 but that's taken. so 8-3. Done.
– deep thought
1 hour ago
Sorry if I ninjaed you! Your reasons for saying it's unique are very much like mine (unsurprisingly) but since I hadn't bothered to write them out carefully I didn't want to claim too much :-).
– Gareth McCaughan♦
1 hour ago
add a comment |
up vote
5
down vote
This appears to work, and I think it's unique but haven't checked super-carefully:
10 -- 13 -- 6 -- 11 -- 8 -- 3 -- 14 -- 9 -- 2 -- 5 -- 12 -- 1 -- 4 -- 7 -- (10)
answered 2 hours ago
Gareth McCaughan♦
59.4k3150230
Was about to post this too, and I'm pretty sure it's unique because: there are 2 or 3 possibilities for the neighbours of each number, if 2 then it's forced, and then we can draw a graph for the remaining and there is only one cycle covering all numbers.
– deep thought
2 hours ago
To expand a bit: 2,11,13,14 can each only be adjacent to two numbers, so that part of the sequence is forced, namely 3-14-9-2-5 and 10-13-6-11-8. 1 could neighbour 4,6,12 but 6 is now "taken" by 13 and 11, so 12-1-4 is forced. 4 could neighbour 9 but 9 is also taken, 1-4-7. 12 could neighbour 7 but that would close off a cycle of length 4. So 12 and 7 are forced: 7-10 and 5-12. 3 could neighbour 10 but that's taken. so 8-3. Done.
– deep thought
1 hour ago
Sorry if I ninjaed you! Your reasons for saying it's unique are very much like mine (unsurprisingly) but since I hadn't bothered to write them out carefully I didn't want to claim too much :-).
– Gareth McCaughan♦
1 hour ago
add a comment |
up vote
5
down vote
up vote
5
down vote
This appears to work, and I think it's unique but haven't checked super-carefully:
10 -- 13 -- 6 -- 11 -- 8 -- 3 -- 14 -- 9 -- 2 -- 5 -- 12 -- 1 -- 4 -- 7 -- (10)
answered 2 hours ago
Gareth McCaughan♦
59.4k3150230
This appears to work, and I think it's unique but haven't checked super-carefully:
10 -- 13 -- 6 -- 11 -- 8 -- 3 -- 14 -- 9 -- 2 -- 5 -- 12 -- 1 -- 4 -- 7 -- (10)
answered 2 hours ago
Gareth McCaughan♦
59.4k3150230
answered 2 hours ago
Gareth McCaughan♦
59.4k3150230
answered 2 hours ago
Gareth McCaughan♦
59.4k3150230
answered 2 hours ago
Gareth McCaughan♦
59.4k3150230
59.4k3150230
Was about to post this too, and I'm pretty sure it's unique because: there are 2 or 3 possibilities for the neighbours of each number, if 2 then it's forced, and then we can draw a graph for the remaining and there is only one cycle covering all numbers.
– deep thought
2 hours ago
To expand a bit: 2,11,13,14 can each only be adjacent to two numbers, so that part of the sequence is forced, namely 3-14-9-2-5 and 10-13-6-11-8. 1 could neighbour 4,6,12 but 6 is now "taken" by 13 and 11, so 12-1-4 is forced. 4 could neighbour 9 but 9 is also taken, 1-4-7. 12 could neighbour 7 but that would close off a cycle of length 4. So 12 and 7 are forced: 7-10 and 5-12. 3 could neighbour 10 but that's taken. so 8-3. Done.
– deep thought
1 hour ago
Sorry if I ninjaed you! Your reasons for saying it's unique are very much like mine (unsurprisingly) but since I hadn't bothered to write them out carefully I didn't want to claim too much :-).
– Gareth McCaughan♦
1 hour ago
add a comment |
Was about to post this too, and I'm pretty sure it's unique because: there are 2 or 3 possibilities for the neighbours of each number, if 2 then it's forced, and then we can draw a graph for the remaining and there is only one cycle covering all numbers.
– deep thought
2 hours ago
To expand a bit: 2,11,13,14 can each only be adjacent to two numbers, so that part of the sequence is forced, namely 3-14-9-2-5 and 10-13-6-11-8. 1 could neighbour 4,6,12 but 6 is now "taken" by 13 and 11, so 12-1-4 is forced. 4 could neighbour 9 but 9 is also taken, 1-4-7. 12 could neighbour 7 but that would close off a cycle of length 4. So 12 and 7 are forced: 7-10 and 5-12. 3 could neighbour 10 but that's taken. so 8-3. Done.
– deep thought
1 hour ago
Sorry if I ninjaed you! Your reasons for saying it's unique are very much like mine (unsurprisingly) but since I hadn't bothered to write them out carefully I didn't want to claim too much :-).
– Gareth McCaughan♦
1 hour ago
Was about to post this too, and I'm pretty sure it's unique because: there are 2 or 3 possibilities for the neighbours of each number, if 2 then it's forced, and then we can draw a graph for the remaining and there is only one cycle covering all numbers.
– deep thought
2 hours ago
Was about to post this too, and I'm pretty sure it's unique because: there are 2 or 3 possibilities for the neighbours of each number, if 2 then it's forced, and then we can draw a graph for the remaining and there is only one cycle covering all numbers.
– deep thought
2 hours ago
To expand a bit: 2,11,13,14 can each only be adjacent to two numbers, so that part of the sequence is forced, namely 3-14-9-2-5 and 10-13-6-11-8. 1 could neighbour 4,6,12 but 6 is now "taken" by 13 and 11, so 12-1-4 is forced. 4 could neighbour 9 but 9 is also taken, 1-4-7. 12 could neighbour 7 but that would close off a cycle of length 4. So 12 and 7 are forced: 7-10 and 5-12. 3 could neighbour 10 but that's taken. so 8-3. Done.
– deep thought
1 hour ago
To expand a bit: 2,11,13,14 can each only be adjacent to two numbers, so that part of the sequence is forced, namely 3-14-9-2-5 and 10-13-6-11-8. 1 could neighbour 4,6,12 but 6 is now "taken" by 13 and 11, so 12-1-4 is forced. 4 could neighbour 9 but 9 is also taken, 1-4-7. 12 could neighbour 7 but that would close off a cycle of length 4. So 12 and 7 are forced: 7-10 and 5-12. 3 could neighbour 10 but that's taken. so 8-3. Done.
– deep thought
1 hour ago
Sorry if I ninjaed you! Your reasons for saying it's unique are very much like mine (unsurprisingly) but since I hadn't bothered to write them out carefully I didn't want to claim too much :-).
– Gareth McCaughan♦
1 hour ago
Sorry if I ninjaed you! Your reasons for saying it's unique are very much like mine (unsurprisingly) but since I hadn't bothered to write them out carefully I didn't want to claim too much :-).
– Gareth McCaughan♦
1 hour ago
add a comment |
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Was this an original question? Or do you have a source?
– Dr Xorile
25 mins ago