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.

Showing 1-4 of 4 results.

A360788 Expansion of Sum_{k>=0} x^k / (1 - (k*x)^3)^(k+1).

Original entry on oeis.org

1, 1, 1, 1, 3, 25, 109, 324, 1135, 8803, 64189, 337854, 1707319, 13421410, 121248893, 894378619, 6082868725, 53046554917, 543432115477, 4989423130739, 42565774604131, 421544374075072, 4781440892689533, 51342685464272591, 522295380717090265
Offset: 0

Views

Author

Seiichi Manyama, Feb 20 2023

Keywords

Crossrefs

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(sum(k=0, N, x^k/(1-(k*x)^3)^(k+1)))
    
  • PARI
    a(n) = sum(k=0, n\3, (n-3*k)^(3*k)*binomial(n-2*k, k));

Formula

a(n) = Sum_{k=0..floor(n/3)} (n-3*k)^(3*k) * binomial(n-2*k,k).

A360834 Expansion of Sum_{k>=0} (k * x)^k / (1 - (k * x)^2)^(k+1).

Original entry on oeis.org

1, 1, 4, 29, 304, 4100, 67520, 1314167, 29520128, 751658635, 21393444864, 673046604600, 23192501108736, 868730852002205, 35145114836811776, 1527192185786650417, 70941146068492943360, 3508043437942077557884, 183989995827118805352448
Offset: 0

Views

Author

Seiichi Manyama, Feb 22 2023

Keywords

Crossrefs

Programs

  • PARI
    my(N=20, x='x+O('x^N)); Vec(sum(k=0, N, (k*x)^k/(1-(k*x)^2)^(k+1)))
    
  • PARI
    a(n) = sum(k=0, n\2, (n-2*k)^n*binomial(n-k, k));

Formula

a(n) = Sum_{k=0..floor(n/2)} (n-2*k)^n * binomial(n-k,k).

A360795 Expansion of Sum_{k>0} x^k / (1 - (k * x)^k)^(k+1).

Original entry on oeis.org

1, 3, 4, 17, 6, 211, 8, 1929, 7300, 22601, 12, 1724809, 14, 6703047, 223678576, 738787345, 18, 65630598229, 20, 2119646503661, 24448573943662, 3423809253371, 24, 21453113652593665, 12016296386718776, 4240253019018225, 8255251542208471048, 67251293544533119589, 30
Offset: 1

Views

Author

Seiichi Manyama, Feb 21 2023

Keywords

Crossrefs

Programs

  • Mathematica
    a[n_] := DivisorSum[n, #^(n-#) * Binomial[# + n/# - 1, #] &]; Array[a, 30] (* Amiram Eldar, Aug 02 2023 *)
  • PARI
    my(N=30, x='x+O('x^N)); Vec(sum(k=1, N, x^k/(1-(k*x)^k)^(k+1)))
    
  • PARI
    a(n) = sumdiv(n, d, d^(n-d)*binomial(d+n/d-1, d));

Formula

a(n) = Sum_{d|n} d^(n-d) * binomial(d+n/d-1,d).
If p is prime, a(p) = 1 + p.

A360812 Expansion of Sum_{k>=0} ( x / (1 - (k * x)^2) )^k.

Original entry on oeis.org

1, 1, 1, 2, 9, 29, 113, 613, 3033, 17010, 110929, 713249, 5061097, 38762873, 302389553, 2544613578, 22404995001, 203762678941, 1960880744337, 19509713674397, 201306862742217, 2166901479447194, 24018963506471921, 275731857268608673, 3271769647891351705
Offset: 0

Views

Author

Seiichi Manyama, Feb 21 2023

Keywords

Crossrefs

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(sum(k=0, N, (x/(1-(k*x)^2))^k))
    
  • PARI
    a(n) = sum(k=0, n\2, (n-2*k)^(2*k)*binomial(n-k-1, k));

Formula

a(n) = Sum_{k=0..floor(n/2)} (n-2*k)^(2*k) * binomial(n-k-1,k).
Showing 1-4 of 4 results.