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 11-15 of 15 results.

A356486 a(n) = (n-1)! * Sum_{d|n} d^n / (d-1)!.

Original entry on oeis.org

1, 5, 29, 358, 3149, 98196, 824263, 73122736, 784270089, 158028202000, 285315299411, 855386690484096, 302875585593853, 5876921233326141376, 111916280261483009775, 73985874496557113890816, 827240282809126652177, 1625215094103508198780449024
Offset: 1

Views

Author

Seiichi Manyama, Aug 09 2022

Keywords

Crossrefs

Programs

  • Mathematica
    a[n_] := (n-1)! * DivisorSum[n, #^n / (#-1)! &]; Array[a, 18] (* Amiram Eldar, Aug 30 2023 *)
  • PARI
    a(n) = (n-1)!*sumdiv(n, d, d^n/(d-1)!);
    
  • PARI
    my(N=20, x='x+O('x^N)); Vec(serlaplace(-sum(k=1, N, log(1-(k*x)^k)/k!)))

Formula

If p is prime, a(p) = p^p + (p-1)!.
E.g.f.: -Sum_{k>0} log(1 - (k * x)^k)/k!.

A354338 a(n) = n! * Sum_{k=1..n} ( Sum_{d|k} 1/(d * (k/d)!) )/(n-k)!.

Original entry on oeis.org

1, 4, 12, 41, 145, 742, 3962, 27659, 215131, 1996356, 17300360, 218809109, 2421142269, 31105286682, 427776526574, 6964677268087, 97708052695959, 1856379196278120, 30362097934331500, 606395795174882161, 12016899266310773097, 261771941015999635310
Offset: 1

Views

Author

Seiichi Manyama, Aug 15 2022

Keywords

Crossrefs

Programs

  • PARI
    a087906(n) = n!*sumdiv(n, d, 1/(d*(n/d)!));
    a(n) = sum(k=1, n, a087906(k)*binomial(n, k));
    
  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(exp(x)*sum(k=1, N, (exp(x^k)-1)/k)))
    
  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(-exp(x)*sum(k=1, N, log(1-x^k)/k!)))

Formula

a(n) = Sum_{k=1..n} A087906(k) * binomial(n,k).
E.g.f.: exp(x) * Sum_{k>0} (exp(x^k) - 1)/k.
E.g.f.: -exp(x) * Sum_{k>0} log(1-x^k)/k!.

A356575 Expansion of e.g.f. ( Product_{k>0} 1/(1-x^k)^(1/k!) )^x.

Original entry on oeis.org

1, 0, 2, 6, 24, 185, 990, 9877, 72968, 824553, 8495560, 102689741, 1317098772, 18729163609, 270642677396, 4396374315075, 73997950572016, 1318896555293137, 24900891903482832, 499312682762581945, 10301544926241347140, 227464062944112566481
Offset: 0

Views

Author

Seiichi Manyama, Aug 12 2022

Keywords

Crossrefs

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(1/prod(k=1, N, (1-x^k)^(1/k!))^x))
    
  • PARI
    a087906(n) = (n-1)!*sumdiv(n, d, 1/(d-1)!);
    a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=sum(j=2, i, j*a087906(j-1)*binomial(i-1, j-1)*v[i-j+1])); v;

Formula

a(0) = 1, a(1) = 0; a(n) = Sum_{k=2..n} k * A087906(k-1) * binomial(n-1,k-1) * a(n-k).

A363736 a(n) = (n-1)! * Sum_{d|n} (-1)^(d+1) / (d-1)!.

Original entry on oeis.org

1, 0, 3, -1, 25, 59, 721, -841, 60481, 15119, 3628801, 12972959, 479001601, 8648639, 134399865601, -218205187201, 20922789888001, 174888473759999, 6402373705728001, -15205972772390401, 3652732042831872001, 14079294028799, 1124000727777607680001
Offset: 1

Views

Author

Seiichi Manyama, Jun 18 2023

Keywords

Crossrefs

Programs

  • Mathematica
    a[n_] := (n-1)! * DivisorSum[n, (-1)^(#+1)/(#-1)! &]; Array[a, 25] (* Amiram Eldar, Jul 03 2023 *)
  • PARI
    a(n) = (n-1)!*sumdiv(n, d, (-1)^(d+1)/(d-1)!);

Formula

E.g.f.: Sum_{k>0} (1 - exp(-x^k))/k.
E.g.f.: Sum_{k>0} (-1)^k * log(1-x^k)/k!.
If p is an odd prime, a(p) = 1 + (p-1)!.

A370608 a(n) = (n-1)! * Sum_{d|n} 1/((d-1)! * (n/d)!^(d-1)).

Original entry on oeis.org

1, 2, 3, 10, 25, 156, 721, 5356, 40881, 366850, 3628801, 40048086, 479001601, 6228391456, 87184121025, 1307724593176, 20922789888001, 355689166978146, 6402373705728001, 121645161595446490, 2432902128489747201, 51090943465394571376, 1124000727777607680001
Offset: 1

Views

Author

Seiichi Manyama, Feb 23 2024

Keywords

Crossrefs

Programs

  • PARI
    a(n) = (n-1)!*sumdiv(n, d, 1/((d-1)!*(n/d)!^(d-1)));
    
  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(sum(k=1, N, (k-1)!*(exp(x^k/k!)-1))))

Formula

If p is prime, a(p) = 1 + (p-1)!.
E.g.f.: Sum_{k>0} (k-1)! * (exp(x^k/k!)-1).
Previous Showing 11-15 of 15 results.