Properties of greatest integer function












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I am curious to know some properties of the floor functions, for instance, $lfloor a cdot x rfloor$, $lfloor a1cdot x1+a2cdot x2 rfloor$, etc. Is there any book that contains such properties ?










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  • $begingroup$
    What kind of properties are you looking for?
    $endgroup$
    – AD.
    Jun 28 '15 at 10:06










  • $begingroup$
    For example, is it true that floor(ax) = afloor(x) for non-negative real number a ? What can you tell if a is negative real ?
    $endgroup$
    – Naveen Crasta
    Jun 28 '15 at 12:55










  • $begingroup$
    There is no such rule, as easy examples shows, please try to find some and you will see why.
    $endgroup$
    – AD.
    Jun 28 '15 at 17:39
















0












$begingroup$


I am curious to know some properties of the floor functions, for instance, $lfloor a cdot x rfloor$, $lfloor a1cdot x1+a2cdot x2 rfloor$, etc. Is there any book that contains such properties ?










share|cite|improve this question











$endgroup$












  • $begingroup$
    What kind of properties are you looking for?
    $endgroup$
    – AD.
    Jun 28 '15 at 10:06










  • $begingroup$
    For example, is it true that floor(ax) = afloor(x) for non-negative real number a ? What can you tell if a is negative real ?
    $endgroup$
    – Naveen Crasta
    Jun 28 '15 at 12:55










  • $begingroup$
    There is no such rule, as easy examples shows, please try to find some and you will see why.
    $endgroup$
    – AD.
    Jun 28 '15 at 17:39














0












0








0





$begingroup$


I am curious to know some properties of the floor functions, for instance, $lfloor a cdot x rfloor$, $lfloor a1cdot x1+a2cdot x2 rfloor$, etc. Is there any book that contains such properties ?










share|cite|improve this question











$endgroup$




I am curious to know some properties of the floor functions, for instance, $lfloor a cdot x rfloor$, $lfloor a1cdot x1+a2cdot x2 rfloor$, etc. Is there any book that contains such properties ?







special-functions






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share|cite|improve this question













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edited Jun 28 '15 at 23:48









iadvd

5,452102656




5,452102656










asked Jun 26 '15 at 21:30









Naveen CrastaNaveen Crasta

134




134












  • $begingroup$
    What kind of properties are you looking for?
    $endgroup$
    – AD.
    Jun 28 '15 at 10:06










  • $begingroup$
    For example, is it true that floor(ax) = afloor(x) for non-negative real number a ? What can you tell if a is negative real ?
    $endgroup$
    – Naveen Crasta
    Jun 28 '15 at 12:55










  • $begingroup$
    There is no such rule, as easy examples shows, please try to find some and you will see why.
    $endgroup$
    – AD.
    Jun 28 '15 at 17:39


















  • $begingroup$
    What kind of properties are you looking for?
    $endgroup$
    – AD.
    Jun 28 '15 at 10:06










  • $begingroup$
    For example, is it true that floor(ax) = afloor(x) for non-negative real number a ? What can you tell if a is negative real ?
    $endgroup$
    – Naveen Crasta
    Jun 28 '15 at 12:55










  • $begingroup$
    There is no such rule, as easy examples shows, please try to find some and you will see why.
    $endgroup$
    – AD.
    Jun 28 '15 at 17:39
















$begingroup$
What kind of properties are you looking for?
$endgroup$
– AD.
Jun 28 '15 at 10:06




$begingroup$
What kind of properties are you looking for?
$endgroup$
– AD.
Jun 28 '15 at 10:06












$begingroup$
For example, is it true that floor(ax) = afloor(x) for non-negative real number a ? What can you tell if a is negative real ?
$endgroup$
– Naveen Crasta
Jun 28 '15 at 12:55




$begingroup$
For example, is it true that floor(ax) = afloor(x) for non-negative real number a ? What can you tell if a is negative real ?
$endgroup$
– Naveen Crasta
Jun 28 '15 at 12:55












$begingroup$
There is no such rule, as easy examples shows, please try to find some and you will see why.
$endgroup$
– AD.
Jun 28 '15 at 17:39




$begingroup$
There is no such rule, as easy examples shows, please try to find some and you will see why.
$endgroup$
– AD.
Jun 28 '15 at 17:39










1 Answer
1






active

oldest

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0












$begingroup$


  • There is Legendre's formula which counts the number of positive integers less than or equal to a number $n$ which are not divisible by any of the first $k$ primes:
    $$begin{align}
    &phi(n,k)=lfloor n rfloor-sum_{p_ile k}leftlfloor dfrac{ n }{(p_i)}rightrfloor+sum_{p_i<p_jle k}leftlfloordfrac{ n}{(p_ip_j)}rightrfloor-sum_{p_i<p_j<p_mle k}leftlfloor dfrac{n}{(p_ip_jp_m)}rightrfloor+dots
    end{align}$$


which tells us that total number of times a prime $p$ divides $n!$ is $$sum_{k=1}^{infty}lfloorfrac{n}{p^k}rfloor$$




  • For positive integers $lfloor sqrt{n}+sqrt{n+1}rfloor=lfloorsqrt{4n+2}rfloor$

  • $lfloor2xrfloor+lfloor2yrfloorge lfloor x rfloor+lfloor y rfloor+lfloor x+y rfloor$

  • $lfloor frac n2 rfloor- lfloor frac{-n}{2} rfloor=n$ for integers $n ge 0$.


You should look up in books on Discrete mathematics or combinatorics. Also see wikipedia link






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  • $begingroup$
    Also, you can refer the following : math.slu.edu/~clair/mcmc/Floor-solutions.pdf
    $endgroup$
    – SARTHAK GUPTA
    Dec 23 '18 at 11:00











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1 Answer
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active

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1 Answer
1






active

oldest

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active

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active

oldest

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0












$begingroup$


  • There is Legendre's formula which counts the number of positive integers less than or equal to a number $n$ which are not divisible by any of the first $k$ primes:
    $$begin{align}
    &phi(n,k)=lfloor n rfloor-sum_{p_ile k}leftlfloor dfrac{ n }{(p_i)}rightrfloor+sum_{p_i<p_jle k}leftlfloordfrac{ n}{(p_ip_j)}rightrfloor-sum_{p_i<p_j<p_mle k}leftlfloor dfrac{n}{(p_ip_jp_m)}rightrfloor+dots
    end{align}$$


which tells us that total number of times a prime $p$ divides $n!$ is $$sum_{k=1}^{infty}lfloorfrac{n}{p^k}rfloor$$




  • For positive integers $lfloor sqrt{n}+sqrt{n+1}rfloor=lfloorsqrt{4n+2}rfloor$

  • $lfloor2xrfloor+lfloor2yrfloorge lfloor x rfloor+lfloor y rfloor+lfloor x+y rfloor$

  • $lfloor frac n2 rfloor- lfloor frac{-n}{2} rfloor=n$ for integers $n ge 0$.


You should look up in books on Discrete mathematics or combinatorics. Also see wikipedia link






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Also, you can refer the following : math.slu.edu/~clair/mcmc/Floor-solutions.pdf
    $endgroup$
    – SARTHAK GUPTA
    Dec 23 '18 at 11:00
















0












$begingroup$


  • There is Legendre's formula which counts the number of positive integers less than or equal to a number $n$ which are not divisible by any of the first $k$ primes:
    $$begin{align}
    &phi(n,k)=lfloor n rfloor-sum_{p_ile k}leftlfloor dfrac{ n }{(p_i)}rightrfloor+sum_{p_i<p_jle k}leftlfloordfrac{ n}{(p_ip_j)}rightrfloor-sum_{p_i<p_j<p_mle k}leftlfloor dfrac{n}{(p_ip_jp_m)}rightrfloor+dots
    end{align}$$


which tells us that total number of times a prime $p$ divides $n!$ is $$sum_{k=1}^{infty}lfloorfrac{n}{p^k}rfloor$$




  • For positive integers $lfloor sqrt{n}+sqrt{n+1}rfloor=lfloorsqrt{4n+2}rfloor$

  • $lfloor2xrfloor+lfloor2yrfloorge lfloor x rfloor+lfloor y rfloor+lfloor x+y rfloor$

  • $lfloor frac n2 rfloor- lfloor frac{-n}{2} rfloor=n$ for integers $n ge 0$.


You should look up in books on Discrete mathematics or combinatorics. Also see wikipedia link






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Also, you can refer the following : math.slu.edu/~clair/mcmc/Floor-solutions.pdf
    $endgroup$
    – SARTHAK GUPTA
    Dec 23 '18 at 11:00














0












0








0





$begingroup$


  • There is Legendre's formula which counts the number of positive integers less than or equal to a number $n$ which are not divisible by any of the first $k$ primes:
    $$begin{align}
    &phi(n,k)=lfloor n rfloor-sum_{p_ile k}leftlfloor dfrac{ n }{(p_i)}rightrfloor+sum_{p_i<p_jle k}leftlfloordfrac{ n}{(p_ip_j)}rightrfloor-sum_{p_i<p_j<p_mle k}leftlfloor dfrac{n}{(p_ip_jp_m)}rightrfloor+dots
    end{align}$$


which tells us that total number of times a prime $p$ divides $n!$ is $$sum_{k=1}^{infty}lfloorfrac{n}{p^k}rfloor$$




  • For positive integers $lfloor sqrt{n}+sqrt{n+1}rfloor=lfloorsqrt{4n+2}rfloor$

  • $lfloor2xrfloor+lfloor2yrfloorge lfloor x rfloor+lfloor y rfloor+lfloor x+y rfloor$

  • $lfloor frac n2 rfloor- lfloor frac{-n}{2} rfloor=n$ for integers $n ge 0$.


You should look up in books on Discrete mathematics or combinatorics. Also see wikipedia link






share|cite|improve this answer









$endgroup$




  • There is Legendre's formula which counts the number of positive integers less than or equal to a number $n$ which are not divisible by any of the first $k$ primes:
    $$begin{align}
    &phi(n,k)=lfloor n rfloor-sum_{p_ile k}leftlfloor dfrac{ n }{(p_i)}rightrfloor+sum_{p_i<p_jle k}leftlfloordfrac{ n}{(p_ip_j)}rightrfloor-sum_{p_i<p_j<p_mle k}leftlfloor dfrac{n}{(p_ip_jp_m)}rightrfloor+dots
    end{align}$$


which tells us that total number of times a prime $p$ divides $n!$ is $$sum_{k=1}^{infty}lfloorfrac{n}{p^k}rfloor$$




  • For positive integers $lfloor sqrt{n}+sqrt{n+1}rfloor=lfloorsqrt{4n+2}rfloor$

  • $lfloor2xrfloor+lfloor2yrfloorge lfloor x rfloor+lfloor y rfloor+lfloor x+y rfloor$

  • $lfloor frac n2 rfloor- lfloor frac{-n}{2} rfloor=n$ for integers $n ge 0$.


You should look up in books on Discrete mathematics or combinatorics. Also see wikipedia link







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Jun 29 '15 at 0:12









Bhaskar VashishthBhaskar Vashishth

7,67212054




7,67212054












  • $begingroup$
    Also, you can refer the following : math.slu.edu/~clair/mcmc/Floor-solutions.pdf
    $endgroup$
    – SARTHAK GUPTA
    Dec 23 '18 at 11:00


















  • $begingroup$
    Also, you can refer the following : math.slu.edu/~clair/mcmc/Floor-solutions.pdf
    $endgroup$
    – SARTHAK GUPTA
    Dec 23 '18 at 11:00
















$begingroup$
Also, you can refer the following : math.slu.edu/~clair/mcmc/Floor-solutions.pdf
$endgroup$
– SARTHAK GUPTA
Dec 23 '18 at 11:00




$begingroup$
Also, you can refer the following : math.slu.edu/~clair/mcmc/Floor-solutions.pdf
$endgroup$
– SARTHAK GUPTA
Dec 23 '18 at 11:00


















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