combinatorics - generating functions Announcing the arrival of Valued Associate #679: Cesar...

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combinatorics - generating functions



Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 23, 2019 at 23:30 UTC (7:30pm US/Eastern)Generating functions word problem(balloons)Combinations of a Multi-set with generating functionsgenerating function combinatorics solutionLearning about generating functions and sequences.Stuck on Generating FunctionsGenerating Functions for MultinomialsFind the number of solutions of the equation using generating functionsGenerating functions $a_{n} =n^{2}$Generating Functions To Deal WithProve Fibonacci Identity using generating functions












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$begingroup$


I need help making an OGF for $1 + x^i + x^{2i}+...+x^{ki}$. I already know how to verify that $1 +x +x^2+...+x^k$ can be written by $({1-x^{k+1}})/({1-x})$. I'm wondering if there is any correlation between the two..?



Any help would be greatly appreciated. Thanks!










share|cite|improve this question









$endgroup$












  • $begingroup$
    Hint: If you wee to substitute $z=x^i$, what would your GF look like then?
    $endgroup$
    – awkward
    Mar 25 at 23:26
















0












$begingroup$


I need help making an OGF for $1 + x^i + x^{2i}+...+x^{ki}$. I already know how to verify that $1 +x +x^2+...+x^k$ can be written by $({1-x^{k+1}})/({1-x})$. I'm wondering if there is any correlation between the two..?



Any help would be greatly appreciated. Thanks!










share|cite|improve this question









$endgroup$












  • $begingroup$
    Hint: If you wee to substitute $z=x^i$, what would your GF look like then?
    $endgroup$
    – awkward
    Mar 25 at 23:26














0












0








0





$begingroup$


I need help making an OGF for $1 + x^i + x^{2i}+...+x^{ki}$. I already know how to verify that $1 +x +x^2+...+x^k$ can be written by $({1-x^{k+1}})/({1-x})$. I'm wondering if there is any correlation between the two..?



Any help would be greatly appreciated. Thanks!










share|cite|improve this question









$endgroup$




I need help making an OGF for $1 + x^i + x^{2i}+...+x^{ki}$. I already know how to verify that $1 +x +x^2+...+x^k$ can be written by $({1-x^{k+1}})/({1-x})$. I'm wondering if there is any correlation between the two..?



Any help would be greatly appreciated. Thanks!







combinatorics generating-functions






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Mar 25 at 23:21









Jeffery RiceJeffery Rice

134




134












  • $begingroup$
    Hint: If you wee to substitute $z=x^i$, what would your GF look like then?
    $endgroup$
    – awkward
    Mar 25 at 23:26


















  • $begingroup$
    Hint: If you wee to substitute $z=x^i$, what would your GF look like then?
    $endgroup$
    – awkward
    Mar 25 at 23:26
















$begingroup$
Hint: If you wee to substitute $z=x^i$, what would your GF look like then?
$endgroup$
– awkward
Mar 25 at 23:26




$begingroup$
Hint: If you wee to substitute $z=x^i$, what would your GF look like then?
$endgroup$
– awkward
Mar 25 at 23:26










2 Answers
2






active

oldest

votes


















1












$begingroup$

Hint: make the substitution $u=x^i$.






share|cite|improve this answer









$endgroup$





















    0












    $begingroup$

    Notice that



    $$1 + x^i + x^{2i} + x^{3i} + ... + x^{ki} = 1 + (x^i)^1 + (x^i)^2 + (x^i)^3 + ... + (x^i)^k$$



    This is a finite geometric series with ratio $x^i$, and thus



    $$1 + x^i + x^{2i} + x^{3i} + ... + x^{ki} = 1 + (x^i)^1 + (x^i)^2 + (x^i)^3 + ... + (x^i)^k = frac{1 - (x^i)^{k+1}}{1 - x^i}$$






    share|cite|improve this answer









    $endgroup$













    • $begingroup$
      Thank you so much. That makes sense, it's just a simple substitution!
      $endgroup$
      – Jeffery Rice
      Mar 25 at 23:38












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    2 Answers
    2






    active

    oldest

    votes








    2 Answers
    2






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    1












    $begingroup$

    Hint: make the substitution $u=x^i$.






    share|cite|improve this answer









    $endgroup$


















      1












      $begingroup$

      Hint: make the substitution $u=x^i$.






      share|cite|improve this answer









      $endgroup$
















        1












        1








        1





        $begingroup$

        Hint: make the substitution $u=x^i$.






        share|cite|improve this answer









        $endgroup$



        Hint: make the substitution $u=x^i$.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Mar 25 at 23:27









        Peter ForemanPeter Foreman

        8,3351321




        8,3351321























            0












            $begingroup$

            Notice that



            $$1 + x^i + x^{2i} + x^{3i} + ... + x^{ki} = 1 + (x^i)^1 + (x^i)^2 + (x^i)^3 + ... + (x^i)^k$$



            This is a finite geometric series with ratio $x^i$, and thus



            $$1 + x^i + x^{2i} + x^{3i} + ... + x^{ki} = 1 + (x^i)^1 + (x^i)^2 + (x^i)^3 + ... + (x^i)^k = frac{1 - (x^i)^{k+1}}{1 - x^i}$$






            share|cite|improve this answer









            $endgroup$













            • $begingroup$
              Thank you so much. That makes sense, it's just a simple substitution!
              $endgroup$
              – Jeffery Rice
              Mar 25 at 23:38
















            0












            $begingroup$

            Notice that



            $$1 + x^i + x^{2i} + x^{3i} + ... + x^{ki} = 1 + (x^i)^1 + (x^i)^2 + (x^i)^3 + ... + (x^i)^k$$



            This is a finite geometric series with ratio $x^i$, and thus



            $$1 + x^i + x^{2i} + x^{3i} + ... + x^{ki} = 1 + (x^i)^1 + (x^i)^2 + (x^i)^3 + ... + (x^i)^k = frac{1 - (x^i)^{k+1}}{1 - x^i}$$






            share|cite|improve this answer









            $endgroup$













            • $begingroup$
              Thank you so much. That makes sense, it's just a simple substitution!
              $endgroup$
              – Jeffery Rice
              Mar 25 at 23:38














            0












            0








            0





            $begingroup$

            Notice that



            $$1 + x^i + x^{2i} + x^{3i} + ... + x^{ki} = 1 + (x^i)^1 + (x^i)^2 + (x^i)^3 + ... + (x^i)^k$$



            This is a finite geometric series with ratio $x^i$, and thus



            $$1 + x^i + x^{2i} + x^{3i} + ... + x^{ki} = 1 + (x^i)^1 + (x^i)^2 + (x^i)^3 + ... + (x^i)^k = frac{1 - (x^i)^{k+1}}{1 - x^i}$$






            share|cite|improve this answer









            $endgroup$



            Notice that



            $$1 + x^i + x^{2i} + x^{3i} + ... + x^{ki} = 1 + (x^i)^1 + (x^i)^2 + (x^i)^3 + ... + (x^i)^k$$



            This is a finite geometric series with ratio $x^i$, and thus



            $$1 + x^i + x^{2i} + x^{3i} + ... + x^{ki} = 1 + (x^i)^1 + (x^i)^2 + (x^i)^3 + ... + (x^i)^k = frac{1 - (x^i)^{k+1}}{1 - x^i}$$







            share|cite|improve this answer












            share|cite|improve this answer



            share|cite|improve this answer










            answered Mar 25 at 23:28









            Eevee TrainerEevee Trainer

            10.6k31842




            10.6k31842












            • $begingroup$
              Thank you so much. That makes sense, it's just a simple substitution!
              $endgroup$
              – Jeffery Rice
              Mar 25 at 23:38


















            • $begingroup$
              Thank you so much. That makes sense, it's just a simple substitution!
              $endgroup$
              – Jeffery Rice
              Mar 25 at 23:38
















            $begingroup$
            Thank you so much. That makes sense, it's just a simple substitution!
            $endgroup$
            – Jeffery Rice
            Mar 25 at 23:38




            $begingroup$
            Thank you so much. That makes sense, it's just a simple substitution!
            $endgroup$
            – Jeffery Rice
            Mar 25 at 23:38


















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