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.

A290158 a(n) = n! * [x^n] exp(-n*x)/(1 + LambertW(-x)).

Original entry on oeis.org

1, 0, 4, -9, 208, -1525, 33516, -463099, 11293248, -231839577, 6517863100, -175791146311, 5723314711632, -189288946716181, 7083626583237036, -275649085963046475, 11724766124450058496, -522717581675749841713, 24981438186138642481404
Offset: 0

Views

Author

Ilya Gutkovskiy, Oct 06 2017

Keywords

Comments

The n-th term of the n-th inverse binomial transform of A000312.

Crossrefs

Programs

  • Mathematica
    Table[n! SeriesCoefficient[Exp[-n x]/(1 + LambertW[-x]), {x, 0, n}], {n, 0, 18}]
  • PARI
    a(n) = (-1)^n*n!*sum(k=0, n\2, n^k*stirling(n-k, k, 2)/(n-k)!); \\ Seiichi Manyama, May 05 2023

Formula

a(n) ~ (-1)^n * n^n / (1 + LambertW(1)). - Vaclav Kotesovec, Oct 06 2017
From Seiichi Manyama, May 05 2023: (Start)
a(n) = (-1)^n * n! * [x^n] exp(n * x * (exp(x) - 1)).
a(n) = (-1)^n * n! * Sum_{k=0..floor(n/2)} n^k * Stirling2(n-k,k)/(n-k)!.
a(n) = [x^n] Sum_{k>=0} (k*x)^k / (1 + n*x)^(k+1).
a(n) = Sum_{k=0..n} (-n)^(n-k) * k^k * binomial(n,k). (End)

A362834 Square array T(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where T(n,k) = (-1)^n * n! * Sum_{j=0..floor(n/2)} k^j * Stirling1(n-j,j)/(n-j)!.

Original entry on oeis.org

1, 1, 0, 1, 0, 0, 1, 0, 2, 0, 1, 0, 4, 3, 0, 1, 0, 6, 6, 20, 0, 1, 0, 8, 9, 64, 90, 0, 1, 0, 10, 12, 132, 300, 594, 0, 1, 0, 12, 15, 224, 630, 2568, 4200, 0, 1, 0, 14, 18, 340, 1080, 6642, 20160, 34544, 0, 1, 0, 16, 21, 480, 1650, 13536, 55440, 193856, 316008, 0
Offset: 0

Views

Author

Seiichi Manyama, May 05 2023

Keywords

Examples

			Square array begins:
  1,  1,   1,   1,    1,    1, ...
  0,  0,   0,   0,    0,    0, ...
  0,  2,   4,   6,    8,   10, ...
  0,  3,   6,   9,   12,   15, ...
  0, 20,  64, 132,  224,  340, ...
  0, 90, 300, 630, 1080, 1650, ...
		

Crossrefs

Columns k=0..3 give: A000007, A066166, A053489, A053490.
Main diagonal gives A318615.
Cf. A361652.

Programs

  • PARI
    T(n, k) = (-1)^n*n!*sum(j=0, n\2, k^j*stirling(n-j, j, 1)/(n-j)!);

Formula

E.g.f. of column k: 1/(1 - x)^(k*x).

A362835 Expansion of e.g.f. 1/(1 + LambertW(x * log(1-x))).

Original entry on oeis.org

1, 0, 2, 3, 56, 270, 4704, 43260, 814736, 11356632, 240848640, 4492204200, 108396245088, 2513538490320, 68878522931568, 1896787592514360, 58622475066067200, 1860520458522196800, 64297710768900261888, 2303738717704104464640
Offset: 0

Views

Author

Seiichi Manyama, May 05 2023

Keywords

Crossrefs

Programs

  • PARI
    my(N=20, x='x+O('x^N)); Vec(serlaplace(1/(1+lambertw(x*log(1-x)))))

Formula

a(n) = (-1)^n * n! * Sum_{k=0..floor(n/2)} k^k * Stirling1(n-k,k)/(n-k)!.

A318616 a(n) = n! * [x^n] (1 - x)^(n*x).

Original entry on oeis.org

1, 0, -4, -9, 160, 1350, -14904, -335160, 1796096, 125615448, 204300000, -64591072920, -735003528192, 41673388751280, 1113912529707264, -30043364514345000, -1703374149711298560, 17822402097051182400, 2856178489894627203072, 12394040043610922716800, -5255899207995216384000000
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 30 2018

Keywords

Crossrefs

Programs

  • Mathematica
    Table[n! SeriesCoefficient[(1 - x)^(n x), {x, 0, n}], {n, 0, 20}]
    Join[{1}, Table[n! Sum[(-1)^k n^(n - k) StirlingS1[k, n - k]/k!, {k, n}], {n, 20}]]

Formula

a(n) = n! * [x^n] exp(-n*x*Sum_{k>=1} x^k/k).
a(n) = n! * Sum_{k=0..n} (-1)^k*n^(n-k)*Stirling1(k,n-k)/k!.
Showing 1-4 of 4 results.