Approximating $sumlimits_{rsubset S}|r|!prodlimits_{xin r}x$












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There is a set $S={x_1, x_2, ..., x_N}.$



I'm trying to approximate this:
$$p(S)=sum_{rsubset S}|r|!prod_{xin r}x$$



I know that:



$$sum_{rsubset S}prod_{xin r}x=prod_{xin S}(1+x)$$



I was wondering if there is a way to approximate $p(S)$ with something.





An idea:
Change $x$ in $prodlimits_{xin S}(1+x)$ to $a(x)x$ so that:



$$prod_{xin S}(1+a(x)x)simsum_{rsubset S}|r|!prod_{xin r}x$$










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    0














    There is a set $S={x_1, x_2, ..., x_N}.$



    I'm trying to approximate this:
    $$p(S)=sum_{rsubset S}|r|!prod_{xin r}x$$



    I know that:



    $$sum_{rsubset S}prod_{xin r}x=prod_{xin S}(1+x)$$



    I was wondering if there is a way to approximate $p(S)$ with something.





    An idea:
    Change $x$ in $prodlimits_{xin S}(1+x)$ to $a(x)x$ so that:



    $$prod_{xin S}(1+a(x)x)simsum_{rsubset S}|r|!prod_{xin r}x$$










    share|cite|improve this question



























      0












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      0







      There is a set $S={x_1, x_2, ..., x_N}.$



      I'm trying to approximate this:
      $$p(S)=sum_{rsubset S}|r|!prod_{xin r}x$$



      I know that:



      $$sum_{rsubset S}prod_{xin r}x=prod_{xin S}(1+x)$$



      I was wondering if there is a way to approximate $p(S)$ with something.





      An idea:
      Change $x$ in $prodlimits_{xin S}(1+x)$ to $a(x)x$ so that:



      $$prod_{xin S}(1+a(x)x)simsum_{rsubset S}|r|!prod_{xin r}x$$










      share|cite|improve this question















      There is a set $S={x_1, x_2, ..., x_N}.$



      I'm trying to approximate this:
      $$p(S)=sum_{rsubset S}|r|!prod_{xin r}x$$



      I know that:



      $$sum_{rsubset S}prod_{xin r}x=prod_{xin S}(1+x)$$



      I was wondering if there is a way to approximate $p(S)$ with something.





      An idea:
      Change $x$ in $prodlimits_{xin S}(1+x)$ to $a(x)x$ so that:



      $$prod_{xin S}(1+a(x)x)simsum_{rsubset S}|r|!prod_{xin r}x$$







      combinatorics discrete-mathematics combinations approximation






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      share|cite|improve this question













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      edited 16 hours ago

























      asked 2 days ago









      Anais

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