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.

A308862 Expansion of e.g.f. 1/(1 - x*(1 + 3*x + x^2)*exp(x)).

Original entry on oeis.org

1, 1, 10, 81, 976, 14505, 258456, 5377897, 127852096, 3419620209, 101625743080, 3322169384721, 118475520287136, 4577175039397753, 190436902905933880, 8489222610046324665, 403657900923994965376, 20393319895130130117729, 1090902632352025316904648
Offset: 0

Views

Author

Ilya Gutkovskiy, Jun 29 2019

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 18; CoefficientList[Series[1/(1 - x (1 + 3 x + x^2) Exp[x]), {x, 0, nmax}], x] Range[0, nmax]!
    a[0] = 1; a[n_] := a[n] = Sum[Binomial[n, k] k^3 a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 18}]
  • PARI
    my(x='x+O('x^25)); Vec(serlaplace(1/(1 - x*(1 + 3*x + x^2)*exp(x)))) \\ Michel Marcus, Mar 10 2022

Formula

E.g.f.: 1 / (1 - Sum_{k>=1} k^3*x^k/k!).
a(0) = 1; a(n) = Sum_{k=1..n} binomial(n,k) * k^3 * a(n-k).
a(n) ~ n! / (r^(n+1) * exp(r) * (1 + 7*r + 6*r^2 + r^3)), where r = 0.33649177041401456061485914122406146158245451810028937972189... is the root of the equation exp(r)*r*(1 + 3*r + r^2) = 1. - Vaclav Kotesovec, Jun 29 2019

A308946 Expansion of e.g.f. 1/(1 - x*(1 + x/2)*exp(x)).

Original entry on oeis.org

1, 1, 5, 30, 244, 2485, 30351, 432502, 7043660, 129050649, 2627117875, 58829021416, 1437117395946, 38032508860177, 1083932872119839, 33098858988564090, 1078083456543449416, 37309607437056658129, 1367138649165397662627, 52879280631976735387588
Offset: 0

Views

Author

Ilya Gutkovskiy, Jul 02 2019

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 19; CoefficientList[Series[1/(1 - x (1 + x/2) Exp[x]), {x, 0, nmax}], x] Range[0, nmax]!
    a[0] = 1; a[n_] := a[n] = Sum[Binomial[n, k] Binomial[k + 1, 2] a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 19}]

Formula

E.g.f.: 1 / (1 - Sum_{k>=1} (k*(k + 1)/2)*x^k/k!).
a(0) = 1; a(n) = Sum_{k=1..n} binomial(n,k) * A000217(k) * a(n-k).
a(n) ~ n! * (2 + r) / ((2 + 4*r + r^2) * r^n), where r = 0.49122518354447387971550543450091640839121607... is the root of the equation exp(r)*r*(2 + r) = 2. - Vaclav Kotesovec, Aug 09 2021

A308863 Expansion of e.g.f. (1 + LambertW(-x))/(1 + 2*LambertW(-x)).

Original entry on oeis.org

1, 1, 6, 57, 736, 11985, 235296, 5403937, 142073856, 4206560769, 138483596800, 5017244970441, 198363105460224, 8498001799768273, 392127481640165376, 19388814120804416625, 1022681739669784231936, 57317273018414456262273, 3401527253966521309200384
Offset: 0

Views

Author

Ilya Gutkovskiy, Jun 29 2019

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 18; CoefficientList[Series[(1 + LambertW[-x])/(1 + 2 LambertW[-x]), {x, 0, nmax}], x] Range[0, nmax]!
    a[0] = 1; a[n_] := a[n] = Sum[Binomial[n, k] k^k a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 18}]

Formula

E.g.f.: 1 / (1 - Sum_{k>=1} k^k*x^k/k!).
a(0) = 1; a(n) = Sum_{k=1..n} binomial(n,k) * k^k * a(n-k).
a(n) ~ sqrt(Pi) * 2^(n - 3/2) * n^(n + 1/2) / exp(n/2). - Vaclav Kotesovec, Jun 29 2019

A335577 a(0) = 1; a(n) = -Sum_{k=1..n} binomial(n,k) * k^2 * a(n-k).

Original entry on oeis.org

1, -1, -2, 9, 32, -285, -1236, 18725, 86176, -2087001, -9204580, 351964569, 1336442304, -83422970917, -231889447076, 26389118293005, 35917342192064, -10722110983670193, 5028963509133756, 5432569724760331841, -14852185163192897120, -3352369390318855889661
Offset: 0

Views

Author

Ilya Gutkovskiy, Jan 26 2021

Keywords

Crossrefs

Programs

  • Mathematica
    a[0] = 1; a[n_] := a[n] = -Sum[Binomial[n, k] k^2 a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 21}]
    nmax = 21; CoefficientList[Series[1/(1 + Exp[x] x (1 + x)), {x, 0, nmax}], x] Range[0, nmax]!

Formula

E.g.f.: 1 / (1 + exp(x) * x * (1 + x)).
E.g.f.: 1 / (1 + Sum_{k>=1} k^2 * x^k / k!).

A336183 a(n) = n^2 + (1/n) * Sum_{k=1..n-1} binomial(n,k) * k * a(k) * (n-k)^2.

Original entry on oeis.org

1, 5, 23, 154, 1389, 15636, 211231, 3329264, 59969097, 1215233380, 27362096211, 677690995488, 18310602210445, 535964033279780, 16894811428737495, 570603293774677696, 20556251540382371217, 786832900592755991364, 31889277719673937849243, 1364231113649221829763200
Offset: 1

Views

Author

Ilya Gutkovskiy, Jul 10 2020

Keywords

Crossrefs

Programs

  • Mathematica
    a[n_] := a[n] = n^2 + (1/n) Sum[Binomial[n, k] k a[k] (n - k)^2, {k, 1, n - 1}]; Table[a[n], {n, 1, 20}]
    nmax = 20; CoefficientList[Series[-Log[1 - Exp[x] x (1 + x)], {x, 0, nmax}], x] Range[0, nmax]! // Rest

Formula

E.g.f.: -log(1 - exp(x) * x * (1 + x)).
E.g.f.: -log(1 - Sum_{k>=1} k^2 * x^k / k!).
a(n) ~ (n-1)! / r^n, where r = A201941 = 0.444130228823966590585466329490984667... is the root of the equation exp(r)*r*(1+r) = 1. - Vaclav Kotesovec, Jul 11 2020

A336960 E.g.f.: 1 / (1 - x * (2 + x) * exp(x)).

Original entry on oeis.org

1, 2, 14, 132, 1676, 26590, 506202, 11242952, 285383240, 8149464954, 258575410190, 9024809281972, 343619185754748, 14173557899208422, 629600469603730562, 29965010056866657600, 1521221783964264806672, 82053967063309770102130, 4686301361507067542636694
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 09 2020

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 18; CoefficientList[Series[1/(1 - x (2 + x) Exp[x]), {x, 0, nmax}], x] Range[0, nmax]!
    a[0] = 1; a[n_] := a[n] = Sum[Binomial[n, k] k (k + 1) a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 18}]

Formula

a(0) = 1; a(n) = Sum_{k=1..n} binomial(n,k) * k * (k + 1) * a(n-k).
a(n) ~ n! * (2 + r) / ((2 + 4*r + r^2) * r^n), where r = 0.31516782494427474715049117135360576083681438371... is the root of the equation exp(r) * r * (2 + r) = 1. - Vaclav Kotesovec, Aug 09 2021
Showing 1-6 of 6 results.