General method to find sum of binomial











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Specifically I want to ask the method to solve
$$sum_{k=0}^n binom{4n+b}{4k}; b=[0,1,2,3]$$



And how to solve series of type
$$sum_{k=0}^n binom{an+b}{ak}; a=[1,2,3,...], b=[0,1,2,...,a-1]$$










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  • series multisection
    – Lord Shark the Unknown
    Nov 22 at 7:38










  • For $4k$, see Arthur T. Benjamin, Jacob N. Scott, Third and fourth binomial coefficients. For $ak$, there is a formula resulting in an $a$-term sum, involving roots of unity; but that's not very explicit in my opinion.
    – darij grinberg
    Nov 22 at 7:38















up vote
1
down vote

favorite
2












Specifically I want to ask the method to solve
$$sum_{k=0}^n binom{4n+b}{4k}; b=[0,1,2,3]$$



And how to solve series of type
$$sum_{k=0}^n binom{an+b}{ak}; a=[1,2,3,...], b=[0,1,2,...,a-1]$$










share|cite|improve this question
























  • series multisection
    – Lord Shark the Unknown
    Nov 22 at 7:38










  • For $4k$, see Arthur T. Benjamin, Jacob N. Scott, Third and fourth binomial coefficients. For $ak$, there is a formula resulting in an $a$-term sum, involving roots of unity; but that's not very explicit in my opinion.
    – darij grinberg
    Nov 22 at 7:38













up vote
1
down vote

favorite
2









up vote
1
down vote

favorite
2






2





Specifically I want to ask the method to solve
$$sum_{k=0}^n binom{4n+b}{4k}; b=[0,1,2,3]$$



And how to solve series of type
$$sum_{k=0}^n binom{an+b}{ak}; a=[1,2,3,...], b=[0,1,2,...,a-1]$$










share|cite|improve this question















Specifically I want to ask the method to solve
$$sum_{k=0}^n binom{4n+b}{4k}; b=[0,1,2,3]$$



And how to solve series of type
$$sum_{k=0}^n binom{an+b}{ak}; a=[1,2,3,...], b=[0,1,2,...,a-1]$$







combinatorics complex-numbers binomial-coefficients






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share|cite|improve this question













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share|cite|improve this question








edited Nov 22 at 7:38

























asked Nov 22 at 7:27









Saurav Singh

183




183












  • series multisection
    – Lord Shark the Unknown
    Nov 22 at 7:38










  • For $4k$, see Arthur T. Benjamin, Jacob N. Scott, Third and fourth binomial coefficients. For $ak$, there is a formula resulting in an $a$-term sum, involving roots of unity; but that's not very explicit in my opinion.
    – darij grinberg
    Nov 22 at 7:38


















  • series multisection
    – Lord Shark the Unknown
    Nov 22 at 7:38










  • For $4k$, see Arthur T. Benjamin, Jacob N. Scott, Third and fourth binomial coefficients. For $ak$, there is a formula resulting in an $a$-term sum, involving roots of unity; but that's not very explicit in my opinion.
    – darij grinberg
    Nov 22 at 7:38
















series multisection
– Lord Shark the Unknown
Nov 22 at 7:38




series multisection
– Lord Shark the Unknown
Nov 22 at 7:38












For $4k$, see Arthur T. Benjamin, Jacob N. Scott, Third and fourth binomial coefficients. For $ak$, there is a formula resulting in an $a$-term sum, involving roots of unity; but that's not very explicit in my opinion.
– darij grinberg
Nov 22 at 7:38




For $4k$, see Arthur T. Benjamin, Jacob N. Scott, Third and fourth binomial coefficients. For $ak$, there is a formula resulting in an $a$-term sum, involving roots of unity; but that's not very explicit in my opinion.
– darij grinberg
Nov 22 at 7:38










1 Answer
1






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up vote
0
down vote



accepted










I am sure that you will enjoy the result !



If $$S_n=sum_{k=0}^n binom{4n+b}{4k}$$ then a CAS gives



$$4S_n=2^{frac{4 n+b}{2} } left((-1)^b, 2^{frac{4 n+b}{2} } cos (pi b)+cos
left(frac{ (4 n+b)pi}{4} right)+(-1)^b cos left(frac{3(4
n+b)pi}{4} right)right)-$$
$$4 binom{4 n+b}{4 n+4} ,
_5F_4left(1,frac{4-b}{4},frac{5-b}{4},frac{6-b}{4},frac
{7-b}{4};frac{4n+5}{4},frac{4n+6}{4},frac{4n+7}{4},frac{4n+8}{4};1right)$$
where appears the generalized hypergeometric function.



For the first values of $b$, the sequences can be found in $OEIS$.



$$left(
begin{array}{cc}
b & text{OEIS sequence} \
0 & text{A070775} \
1 & text{A090407} \
2 & text{A001025} \
3 & text{A090408}
end{array}
right)$$

Be sure that I did not make this by myself.






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    1 Answer
    1






    active

    oldest

    votes








    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes








    up vote
    0
    down vote



    accepted










    I am sure that you will enjoy the result !



    If $$S_n=sum_{k=0}^n binom{4n+b}{4k}$$ then a CAS gives



    $$4S_n=2^{frac{4 n+b}{2} } left((-1)^b, 2^{frac{4 n+b}{2} } cos (pi b)+cos
    left(frac{ (4 n+b)pi}{4} right)+(-1)^b cos left(frac{3(4
    n+b)pi}{4} right)right)-$$
    $$4 binom{4 n+b}{4 n+4} ,
    _5F_4left(1,frac{4-b}{4},frac{5-b}{4},frac{6-b}{4},frac
    {7-b}{4};frac{4n+5}{4},frac{4n+6}{4},frac{4n+7}{4},frac{4n+8}{4};1right)$$
    where appears the generalized hypergeometric function.



    For the first values of $b$, the sequences can be found in $OEIS$.



    $$left(
    begin{array}{cc}
    b & text{OEIS sequence} \
    0 & text{A070775} \
    1 & text{A090407} \
    2 & text{A001025} \
    3 & text{A090408}
    end{array}
    right)$$

    Be sure that I did not make this by myself.






    share|cite|improve this answer



























      up vote
      0
      down vote



      accepted










      I am sure that you will enjoy the result !



      If $$S_n=sum_{k=0}^n binom{4n+b}{4k}$$ then a CAS gives



      $$4S_n=2^{frac{4 n+b}{2} } left((-1)^b, 2^{frac{4 n+b}{2} } cos (pi b)+cos
      left(frac{ (4 n+b)pi}{4} right)+(-1)^b cos left(frac{3(4
      n+b)pi}{4} right)right)-$$
      $$4 binom{4 n+b}{4 n+4} ,
      _5F_4left(1,frac{4-b}{4},frac{5-b}{4},frac{6-b}{4},frac
      {7-b}{4};frac{4n+5}{4},frac{4n+6}{4},frac{4n+7}{4},frac{4n+8}{4};1right)$$
      where appears the generalized hypergeometric function.



      For the first values of $b$, the sequences can be found in $OEIS$.



      $$left(
      begin{array}{cc}
      b & text{OEIS sequence} \
      0 & text{A070775} \
      1 & text{A090407} \
      2 & text{A001025} \
      3 & text{A090408}
      end{array}
      right)$$

      Be sure that I did not make this by myself.






      share|cite|improve this answer

























        up vote
        0
        down vote



        accepted







        up vote
        0
        down vote



        accepted






        I am sure that you will enjoy the result !



        If $$S_n=sum_{k=0}^n binom{4n+b}{4k}$$ then a CAS gives



        $$4S_n=2^{frac{4 n+b}{2} } left((-1)^b, 2^{frac{4 n+b}{2} } cos (pi b)+cos
        left(frac{ (4 n+b)pi}{4} right)+(-1)^b cos left(frac{3(4
        n+b)pi}{4} right)right)-$$
        $$4 binom{4 n+b}{4 n+4} ,
        _5F_4left(1,frac{4-b}{4},frac{5-b}{4},frac{6-b}{4},frac
        {7-b}{4};frac{4n+5}{4},frac{4n+6}{4},frac{4n+7}{4},frac{4n+8}{4};1right)$$
        where appears the generalized hypergeometric function.



        For the first values of $b$, the sequences can be found in $OEIS$.



        $$left(
        begin{array}{cc}
        b & text{OEIS sequence} \
        0 & text{A070775} \
        1 & text{A090407} \
        2 & text{A001025} \
        3 & text{A090408}
        end{array}
        right)$$

        Be sure that I did not make this by myself.






        share|cite|improve this answer














        I am sure that you will enjoy the result !



        If $$S_n=sum_{k=0}^n binom{4n+b}{4k}$$ then a CAS gives



        $$4S_n=2^{frac{4 n+b}{2} } left((-1)^b, 2^{frac{4 n+b}{2} } cos (pi b)+cos
        left(frac{ (4 n+b)pi}{4} right)+(-1)^b cos left(frac{3(4
        n+b)pi}{4} right)right)-$$
        $$4 binom{4 n+b}{4 n+4} ,
        _5F_4left(1,frac{4-b}{4},frac{5-b}{4},frac{6-b}{4},frac
        {7-b}{4};frac{4n+5}{4},frac{4n+6}{4},frac{4n+7}{4},frac{4n+8}{4};1right)$$
        where appears the generalized hypergeometric function.



        For the first values of $b$, the sequences can be found in $OEIS$.



        $$left(
        begin{array}{cc}
        b & text{OEIS sequence} \
        0 & text{A070775} \
        1 & text{A090407} \
        2 & text{A001025} \
        3 & text{A090408}
        end{array}
        right)$$

        Be sure that I did not make this by myself.







        share|cite|improve this answer














        share|cite|improve this answer



        share|cite|improve this answer








        edited Nov 22 at 12:08

























        answered Nov 22 at 10:40









        Claude Leibovici

        117k1156131




        117k1156131






























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