cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Previous Showing 21-24 of 24 results.

A047644 Expansion of (Product_{j>=1} (1-(-x)^j) - 1)^19 in powers of x.

Original entry on oeis.org

1, -19, 171, -969, 3857, -11286, 24206, -34542, 14706, 83011, -294880, 569753, -680694, 220286, 1198672, -3502612, 5661867, -5571579, 791350, 9721976, -23494393, 33415357, -29225230, 2352751, 47086598, -104517176, 140834118, -121255530
Offset: 19

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Author

Keywords

Crossrefs

Programs

  • Magma
    m:=80;
    R:=PowerSeriesRing(Integers(), m);
    Coefficients(R!( ((&*[1-(-x)^j: j in [1..m+2]]) -1)^(19) )); // G. C. Greubel, Sep 07 2023
    
  • Maple
    g:= proc(n) option remember; `if`(n=0, 1, add(add([-d, d, -2*d, d]
          [1+irem(d, 4)], d=numtheory[divisors](j))*g(n-j), j=1..n)/n)
        end:
    b:= proc(n, k) option remember; `if`(k=0, 1, `if`(k=1, `if`(n=0, 0, g(n)),
          (q-> add(b(j, q)*b(n-j, k-q), j=0..n))(iquo(k, 2))))
        end:
    a:= n-> b(n, 19):
    seq(a(n), n=19..46);  # Alois P. Heinz, Feb 07 2021
  • Mathematica
    nmax=46; CoefficientList[Series[(Product[(1-(-x)^j), {j,nmax}] - 1)^19, {x,0,nmax}], x]//Drop[#, 19] & (* Ilya Gutkovskiy, Feb 07 2021 *)
    With[{k=19}, Drop[CoefficientList[Series[(QPochhammer[-x] -1)^k, {x,0, 75}], x], k]] (* G. C. Greubel, Sep 07 2023 *)
  • PARI
    my(x='x+O('x^35)); Vec((eta(-x)-1)^19) \\ Joerg Arndt, Sep 07 2023
  • SageMath
    from sage.modular.etaproducts import qexp_eta
    m=75; k=19;
    def f(k,x): return (-1 + qexp_eta(QQ[['q']], m+2).subs(q=-x) )^k
    def A047644_list(prec):
        P. = PowerSeriesRing(QQ, prec)
        return P( f(k,x) ).list()
    a=A047644_list(m); a[k:] # G. C. Greubel, Sep 07 2023
    

Formula

a(n) = [x^n]( QPochhammer(-x) - 1 )^19. - G. C. Greubel, Sep 07 2023

Extensions

Definition and offset edited by Ilya Gutkovskiy, Feb 07 2021

A047646 Expansion of (Product_{j>=1} (1-(-x)^j) - 1)^21 in powers of x.

Original entry on oeis.org

1, -21, 210, -1330, 5964, -19929, 50253, -91920, 97965, 51604, -526659, 1389297, -2280320, 2118690, 769065, -7613319, 17220042, -23999430, 18024405, 10748850, -63778953, 124134772, -152793270, 99072120, 71722224, -341062407, 610085721
Offset: 21

Views

Author

Keywords

Crossrefs

Programs

  • Magma
    m:=80;
    R:=PowerSeriesRing(Integers(), m);
    Coefficients(R!( ((&*[1-(-x)^j: j in [1..m+2]]) -1)^(21) )); // G. C. Greubel, Sep 06 2023
    
  • Maple
    g:= proc(n) option remember; `if`(n=0, 1, add(add([-d, d, -2*d, d]
          [1+irem(d, 4)], d=numtheory[divisors](j))*g(n-j), j=1..n)/n)
        end:
    b:= proc(n, k) option remember; `if`(k=0, 1, `if`(k=1, `if`(n=0, 0, g(n)),
          (q-> add(b(j, q)*b(n-j, k-q), j=0..n))(iquo(k, 2))))
        end:
    a:= n-> b(n, 21):
    seq(a(n), n=21..47);  # Alois P. Heinz, Feb 07 2021
  • Mathematica
    nmax=47; CoefficientList[Series[(Product[(1-(-x)^j), {j,nmax}] -1)^21, {x, 0, nmax}], x]//Drop[#, 21] & (* Ilya Gutkovskiy, Feb 07 2021 *)
    With[{k=21}, Drop[CoefficientList[Series[(QPochhammer[-x] - 1)^k, {x,0, 75}], x], k]] (* G. C. Greubel, Sep 06 2023 *)
  • PARI
    my(N=44, x='x+O('x^N)); Vec((eta(-x)-1)^21) \\ Joerg Arndt, Sep 06 2023
  • SageMath
    from sage.modular.etaproducts import qexp_eta
    m=75; k=21;
    def f(k,x): return (-1 + qexp_eta(QQ[['q']], m+2).subs(q=-x) )^k
    def A047646_list(prec):
        P. = PowerSeriesRing(QQ, prec)
        return P( f(k,x) ).list()
    a=A047646_list(m); a[k:] # G. C. Greubel, Sep 06 2023
    

Formula

a(n) = [x^n]( QPochhammer(-x) - 1 )^21. - G. C. Greubel, Sep 06 2023

Extensions

Definition and offset edited by Ilya Gutkovskiy, Feb 07 2021

A047647 Expansion of (Product_{j>=1} (1-(-x)^j) - 1)^22 in powers of x.

Original entry on oeis.org

1, -22, 231, -1540, 7293, -25872, 69971, -140822, 183711, -25102, -634480, 2027804, -3817814, 4439116, -919600, -9829270, 27660479, -44779042, 43632974, -1898820, -92518261, 219961214, -313463842, 267448104, 15757973, -547042056, 1173033400
Offset: 22

Views

Author

Keywords

Crossrefs

Programs

  • Magma
    m:=75;
    R:=PowerSeriesRing(Integers(), m);
    Coefficients(R!( ((&*[1-(-x)^j: j in [1..m+2]]) -1)^(22) )); // G. C. Greubel, Sep 05 2023
    
  • Maple
    g:= proc(n) option remember; `if`(n=0, 1, add(add([-d, d, -2*d, d]
          [1+irem(d, 4)], d=numtheory[divisors](j))*g(n-j), j=1..n)/n)
        end:
    b:= proc(n, k) option remember; `if`(k=0, 1, `if`(k=1, `if`(n=0, 0, g(n)),
          (q-> add(b(j, q)*b(n-j, k-q), j=0..n))(iquo(k, 2))))
        end:
    a:= n-> b(n, 22):
    seq(a(n), n=22..48);  # Alois P. Heinz, Feb 07 2021
  • Mathematica
    nmax=48; CoefficientList[Series[(Product[(1-(-x)^j), {j,nmax}] - 1)^22, {x, 0, nmax}], x]//Drop[#, 22] & (* Ilya Gutkovskiy, Feb 07 2021 *)
    With[{k=22}, Drop[CoefficientList[Series[(QPochhammer[-x] -1)^k, {x,0, 75}], x], k]] (* G. C. Greubel, Sep 05 2023 *)
  • PARI
    my(N=55, x='x+O('x^N)); Vec((eta(-x)-1)^22) \\ Michel Marcus, Sep 05 2023
  • SageMath
    from sage.modular.etaproducts import qexp_eta
    m=75; k=22;
    def f(k,x): return (-1 + qexp_eta(QQ[['q']], m+2).subs(q=-x) )^k
    def A047647_list(prec):
        P. = PowerSeriesRing(QQ, prec)
        return P( f(k,x) ).list()
    a=A047647_list(m); a[k:] # G. C. Greubel, Sep 05 2023
    

Formula

a(n) = [x^n]( QPochhammer(-x) - 1 )^22. - G. C. Greubel, Sep 05 2023

Extensions

Definition and offset edited by Ilya Gutkovskiy, Feb 07 2021

A341263 Coefficient of x^(2*n) in (-1 + Product_{k>=1} (1 - x^k))^n.

Original entry on oeis.org

1, -1, 1, -1, -3, 19, -65, 181, -419, 755, -749, -1530, 12255, -47477, 141065, -343526, 660941, -770917, -911369, 9721976, -40135713, 124134772, -313463842, 631382751, -824406065, -492101356, 8192253811, -35948431288, 115087580857, -299576625051, 627027769120, -894734468883
Offset: 0

Views

Author

Ilya Gutkovskiy, Feb 07 2021

Keywords

Crossrefs

Programs

  • Maple
    g:= proc(n) option remember; `if`(n=0, 1, add(add(
         -d, d=numtheory[divisors](j))*g(n-j), j=1..n)/n)
        end:
    b:= proc(n, k) option remember; `if`(k=0, 1, `if`(k=1, g(n+1),
          (q-> add(b(j, q)*b(n-j, k-q), j=0..n))(iquo(k, 2))))
        end:
    a:= n-> b(n$2):
    seq(a(n), n=0..31);  # Alois P. Heinz, Feb 07 2021
  • Mathematica
    Table[SeriesCoefficient[(-1 + QPochhammer[x, x])^n, {x, 0, 2 n}], {n, 0, 31}]
    A[n_, k_] := A[n, k] = If[n == 0, 1, -k Sum[A[n - j, k] DivisorSigma[1, j], {j, 1, n}]/n]; T[n_, k_] := Sum[(-1)^i Binomial[k, i] A[n, k - i], {i, 0, k}];
    Table[T[2 n, n], {n, 0, 31}]
Previous Showing 21-24 of 24 results.