Is it possible to find 2014 distinct positive integers whose sum is divisible by each of them?
$begingroup$
Is it possible to find 2014 distinct positive integers whose sum is divisible by each of them?
I'm not really sure how to even approach this question.
Source: Washington's Monthly Math Hour, 2014
discrete-mathematics intuition pigeonhole-principle
New contributor
$endgroup$
add a comment |
$begingroup$
Is it possible to find 2014 distinct positive integers whose sum is divisible by each of them?
I'm not really sure how to even approach this question.
Source: Washington's Monthly Math Hour, 2014
discrete-mathematics intuition pigeonhole-principle
New contributor
$endgroup$
$begingroup$
I cant even find two.
$endgroup$
– Rudi_Birnbaum
2 hours ago
1
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@Rudi_Birnbaum irrelevant. $2,4,6,12$ are all divisors of $2+4+6+12$.
$endgroup$
– JMoravitz
2 hours ago
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Well, at least I can find three… $1+2+3$
$endgroup$
– Wolfgang Kais
2 hours ago
$begingroup$
@JMoravitz humor?
$endgroup$
– Rudi_Birnbaum
2 hours ago
add a comment |
$begingroup$
Is it possible to find 2014 distinct positive integers whose sum is divisible by each of them?
I'm not really sure how to even approach this question.
Source: Washington's Monthly Math Hour, 2014
discrete-mathematics intuition pigeonhole-principle
New contributor
$endgroup$
Is it possible to find 2014 distinct positive integers whose sum is divisible by each of them?
I'm not really sure how to even approach this question.
Source: Washington's Monthly Math Hour, 2014
discrete-mathematics intuition pigeonhole-principle
discrete-mathematics intuition pigeonhole-principle
New contributor
New contributor
New contributor
asked 2 hours ago
Arvin DingArvin Ding
84
84
New contributor
New contributor
$begingroup$
I cant even find two.
$endgroup$
– Rudi_Birnbaum
2 hours ago
1
$begingroup$
@Rudi_Birnbaum irrelevant. $2,4,6,12$ are all divisors of $2+4+6+12$.
$endgroup$
– JMoravitz
2 hours ago
$begingroup$
Well, at least I can find three… $1+2+3$
$endgroup$
– Wolfgang Kais
2 hours ago
$begingroup$
@JMoravitz humor?
$endgroup$
– Rudi_Birnbaum
2 hours ago
add a comment |
$begingroup$
I cant even find two.
$endgroup$
– Rudi_Birnbaum
2 hours ago
1
$begingroup$
@Rudi_Birnbaum irrelevant. $2,4,6,12$ are all divisors of $2+4+6+12$.
$endgroup$
– JMoravitz
2 hours ago
$begingroup$
Well, at least I can find three… $1+2+3$
$endgroup$
– Wolfgang Kais
2 hours ago
$begingroup$
@JMoravitz humor?
$endgroup$
– Rudi_Birnbaum
2 hours ago
$begingroup$
I cant even find two.
$endgroup$
– Rudi_Birnbaum
2 hours ago
$begingroup$
I cant even find two.
$endgroup$
– Rudi_Birnbaum
2 hours ago
1
1
$begingroup$
@Rudi_Birnbaum irrelevant. $2,4,6,12$ are all divisors of $2+4+6+12$.
$endgroup$
– JMoravitz
2 hours ago
$begingroup$
@Rudi_Birnbaum irrelevant. $2,4,6,12$ are all divisors of $2+4+6+12$.
$endgroup$
– JMoravitz
2 hours ago
$begingroup$
Well, at least I can find three… $1+2+3$
$endgroup$
– Wolfgang Kais
2 hours ago
$begingroup$
Well, at least I can find three… $1+2+3$
$endgroup$
– Wolfgang Kais
2 hours ago
$begingroup$
@JMoravitz humor?
$endgroup$
– Rudi_Birnbaum
2 hours ago
$begingroup$
@JMoravitz humor?
$endgroup$
– Rudi_Birnbaum
2 hours ago
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
Hint: $2,4,6$ are all divisors of $2+4+6=12$. Similarly $2+4+6+12$ are all divisors of $2+4+6+12=24$
So too are $2,4,6,12,24$ all divisors of $2+4+6+12+24$
$~$
Claim: Let $x_1=2, x_2=4, x_3=6$ and let $x_{n+1} = sumlimits_{k=1}^n x_k$ for each $ngeq 3$. You have that $x_imid sumlimits_{k=1}^nx_k$ for all $ileq n$ for all $ngeq 3$.
$endgroup$
add a comment |
$begingroup$
$$begin{align}
1+2+3&=6\
1+2+3+6&=12\
1+2+3+6+12&=24\
vdots
end{align}$$
$endgroup$
$begingroup$
We can say that the $2014$ numbers produced this way are $1,2,3$ and $3cdot 2^k$ for $k in [1,2011]$
$endgroup$
– Ross Millikan
2 hours ago
add a comment |
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2 Answers
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$begingroup$
Hint: $2,4,6$ are all divisors of $2+4+6=12$. Similarly $2+4+6+12$ are all divisors of $2+4+6+12=24$
So too are $2,4,6,12,24$ all divisors of $2+4+6+12+24$
$~$
Claim: Let $x_1=2, x_2=4, x_3=6$ and let $x_{n+1} = sumlimits_{k=1}^n x_k$ for each $ngeq 3$. You have that $x_imid sumlimits_{k=1}^nx_k$ for all $ileq n$ for all $ngeq 3$.
$endgroup$
add a comment |
$begingroup$
Hint: $2,4,6$ are all divisors of $2+4+6=12$. Similarly $2+4+6+12$ are all divisors of $2+4+6+12=24$
So too are $2,4,6,12,24$ all divisors of $2+4+6+12+24$
$~$
Claim: Let $x_1=2, x_2=4, x_3=6$ and let $x_{n+1} = sumlimits_{k=1}^n x_k$ for each $ngeq 3$. You have that $x_imid sumlimits_{k=1}^nx_k$ for all $ileq n$ for all $ngeq 3$.
$endgroup$
add a comment |
$begingroup$
Hint: $2,4,6$ are all divisors of $2+4+6=12$. Similarly $2+4+6+12$ are all divisors of $2+4+6+12=24$
So too are $2,4,6,12,24$ all divisors of $2+4+6+12+24$
$~$
Claim: Let $x_1=2, x_2=4, x_3=6$ and let $x_{n+1} = sumlimits_{k=1}^n x_k$ for each $ngeq 3$. You have that $x_imid sumlimits_{k=1}^nx_k$ for all $ileq n$ for all $ngeq 3$.
$endgroup$
Hint: $2,4,6$ are all divisors of $2+4+6=12$. Similarly $2+4+6+12$ are all divisors of $2+4+6+12=24$
So too are $2,4,6,12,24$ all divisors of $2+4+6+12+24$
$~$
Claim: Let $x_1=2, x_2=4, x_3=6$ and let $x_{n+1} = sumlimits_{k=1}^n x_k$ for each $ngeq 3$. You have that $x_imid sumlimits_{k=1}^nx_k$ for all $ileq n$ for all $ngeq 3$.
answered 2 hours ago
JMoravitzJMoravitz
48.2k33886
48.2k33886
add a comment |
add a comment |
$begingroup$
$$begin{align}
1+2+3&=6\
1+2+3+6&=12\
1+2+3+6+12&=24\
vdots
end{align}$$
$endgroup$
$begingroup$
We can say that the $2014$ numbers produced this way are $1,2,3$ and $3cdot 2^k$ for $k in [1,2011]$
$endgroup$
– Ross Millikan
2 hours ago
add a comment |
$begingroup$
$$begin{align}
1+2+3&=6\
1+2+3+6&=12\
1+2+3+6+12&=24\
vdots
end{align}$$
$endgroup$
$begingroup$
We can say that the $2014$ numbers produced this way are $1,2,3$ and $3cdot 2^k$ for $k in [1,2011]$
$endgroup$
– Ross Millikan
2 hours ago
add a comment |
$begingroup$
$$begin{align}
1+2+3&=6\
1+2+3+6&=12\
1+2+3+6+12&=24\
vdots
end{align}$$
$endgroup$
$$begin{align}
1+2+3&=6\
1+2+3+6&=12\
1+2+3+6+12&=24\
vdots
end{align}$$
answered 2 hours ago
saulspatzsaulspatz
17k31434
17k31434
$begingroup$
We can say that the $2014$ numbers produced this way are $1,2,3$ and $3cdot 2^k$ for $k in [1,2011]$
$endgroup$
– Ross Millikan
2 hours ago
add a comment |
$begingroup$
We can say that the $2014$ numbers produced this way are $1,2,3$ and $3cdot 2^k$ for $k in [1,2011]$
$endgroup$
– Ross Millikan
2 hours ago
$begingroup$
We can say that the $2014$ numbers produced this way are $1,2,3$ and $3cdot 2^k$ for $k in [1,2011]$
$endgroup$
– Ross Millikan
2 hours ago
$begingroup$
We can say that the $2014$ numbers produced this way are $1,2,3$ and $3cdot 2^k$ for $k in [1,2011]$
$endgroup$
– Ross Millikan
2 hours ago
add a comment |
Arvin Ding is a new contributor. Be nice, and check out our Code of Conduct.
Arvin Ding is a new contributor. Be nice, and check out our Code of Conduct.
Arvin Ding is a new contributor. Be nice, and check out our Code of Conduct.
Arvin Ding is a new contributor. Be nice, and check out our Code of Conduct.
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$begingroup$
I cant even find two.
$endgroup$
– Rudi_Birnbaum
2 hours ago
1
$begingroup$
@Rudi_Birnbaum irrelevant. $2,4,6,12$ are all divisors of $2+4+6+12$.
$endgroup$
– JMoravitz
2 hours ago
$begingroup$
Well, at least I can find three… $1+2+3$
$endgroup$
– Wolfgang Kais
2 hours ago
$begingroup$
@JMoravitz humor?
$endgroup$
– Rudi_Birnbaum
2 hours ago