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 1-6 of 6 results.

A358081 Expansion of e.g.f. 1/(1 - x^3 * exp(x)).

Original entry on oeis.org

1, 0, 0, 6, 24, 60, 840, 10290, 80976, 847224, 13306320, 190271070, 2677088040, 46082426676, 874515884424, 16582066303530, 336875275380000, 7539189088358640, 176554878235711776, 4295134487197296054, 111114287924643309240, 3036073975138066955820
Offset: 0

Views

Author

Seiichi Manyama, Oct 30 2022

Keywords

Crossrefs

Programs

  • Mathematica
    With[{nn=30},CoefficientList[Series[1/(1-x^3 Exp[x]),{x,0,nn}],x] Range[0,nn]!] (* Harvey P. Dale, Aug 12 2025 *)
  • PARI
    my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1-x^3*exp(x))))
    
  • PARI
    a(n) = n!*sum(k=0, n\3, k^(n-3*k)/(n-3*k)!);

Formula

a(n) = n! * Sum_{k=0..floor(n/3)} k^(n - 3*k)/(n - 3*k)!.
a(n) ~ n! / ((1 + LambertW(1/3)) * 3^(n+1) * LambertW(1/3)^n). - Vaclav Kotesovec, Oct 30 2022

A370984 Expansion of e.g.f. (1/x) * Series_Reversion( x*(1 - x^2*exp(x)) ).

Original entry on oeis.org

1, 0, 2, 6, 84, 860, 14430, 257082, 5678456, 140241096, 3952791450, 123539438990, 4266378769092, 160943793753756, 6592371152535350, 291260465060881890, 13809548247503299440, 699362685890810753552, 37679514498664685654706
Offset: 0

Views

Author

Seiichi Manyama, Mar 06 2024

Keywords

Crossrefs

Programs

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

Formula

a(n) = (1/(n+1)) * Sum_{k=0..floor(n/2)} k^(n-2*k) * (n+k)!/(k! * (n-2*k)!).

A366459 Expansion of e.g.f. -log(1 - x^2 * exp(x)).

Original entry on oeis.org

0, 0, 2, 6, 24, 140, 990, 8442, 84056, 955656, 12227130, 173812430, 2717859012, 46362339036, 856770362630, 17050946225250, 363576478312560, 8269357341437072, 199837364514425586, 5113346326011170838, 138106722548779770620, 3926456810081828991780
Offset: 0

Views

Author

Seiichi Manyama, Dec 14 2023

Keywords

Crossrefs

Programs

  • PARI
    a(n) = n!*sum(k=1, n\2, k^(n-2*k-1)/(n-2*k)!);

Formula

a(n) = n! * Sum_{k=1..floor(n/2)} k^(n-2*k-1)/(n-2*k)!.
a(n) ~ (n-1)! / (2^n *LambertW(1/2)^n). - Vaclav Kotesovec, Dec 29 2023

A375629 Expansion of e.g.f. exp(2*x) / (1 - x^2 * exp(x)).

Original entry on oeis.org

1, 2, 6, 26, 148, 1052, 8974, 89294, 1015480, 12991832, 184682554, 2887850858, 49261993444, 910356170804, 18117379906630, 386315966673638, 8786555389140976, 212335975835710256, 5433155029435593970, 146744457899073450050, 4172032796528725318876
Offset: 0

Views

Author

Seiichi Manyama, Aug 21 2024

Keywords

Crossrefs

Programs

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

Formula

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

A377532 Expansion of e.g.f. 1/(1 - x^2 * exp(x))^3.

Original entry on oeis.org

1, 0, 6, 18, 180, 1500, 15930, 191646, 2580648, 38683224, 636068430, 11392350090, 220658360076, 4594593295188, 102333126352002, 2427278515815510, 61079333377870800, 1625065147997303856, 45576552142354413078, 1343802083242003570818, 41552482139458105525620
Offset: 0

Views

Author

Seiichi Manyama, Oct 31 2024

Keywords

Crossrefs

Programs

  • PARI
    a(n) = n!*sum(k=0, n\2, k^(n-2*k)*binomial(k+2, 2)/(n-2*k)!);

Formula

a(n) = n! * Sum_{k=0..floor(n/2)} k^(n-2*k) * binomial(k+2,2)/(n-2*k)!.
a(n) ~ n! * n^2 / ((1 + LambertW(1/2))^3 * 2^(n+4) * LambertW(1/2)^n). - Vaclav Kotesovec, Oct 31 2024

A377531 Expansion of e.g.f. 1/(1 - x^2 * exp(x))^2.

Original entry on oeis.org

1, 0, 4, 12, 96, 760, 7260, 80724, 1008112, 14079888, 216881460, 3652767580, 66773963784, 1316433381432, 27840054610732, 628626642921060, 15093709672205280, 383989133237230624, 10317497504580922212, 291958800400148127660, 8678485827979443326200
Offset: 0

Views

Author

Seiichi Manyama, Oct 31 2024

Keywords

Crossrefs

Programs

  • PARI
    a(n) = n!*sum(k=0, n\2, (k+1)*k^(n-2*k)/(n-2*k)!);

Formula

a(n) = n! * Sum_{k=0..floor(n/2)} (k+1) * k^(n-2*k)/(n-2*k)!.
a(n) ~ n! * n / ((1 + LambertW(1/2))^2 * 2^(n+2) * LambertW(1/2)^n). - Vaclav Kotesovec, Oct 31 2024
Showing 1-6 of 6 results.