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 1-3 of 3 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)

A290824 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where column k is the expansion of e.g.f. exp(k*x)/(1 + LambertW(-x)).

Original entry on oeis.org

1, 1, 1, 1, 2, 4, 1, 3, 7, 27, 1, 4, 12, 43, 256, 1, 5, 19, 71, 393, 3125, 1, 6, 28, 117, 616, 4721, 46656, 1, 7, 39, 187, 985, 7197, 69853, 823543, 1, 8, 52, 287, 1584, 11123, 105052, 1225757, 16777216, 1, 9, 67, 423, 2521, 17429, 159093, 1829291, 24866481, 387420489, 1, 10, 84, 601, 3928, 27525, 243256, 2740111, 36922928, 572410513, 10000000000
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 11 2017

Keywords

Comments

A(n,k) is the k-th binomial transform of A000312 evaluated at n.

Examples

			E.g.f. of column k: A_k(x) = 1 + (k + 1)*x/1! + (k^2 + 2*k + 4)*x^2/2! + (k^3 + 3*k^2 + 12*k + 27)*x^3/3! + (k^4 + 4*k^3 + 24*k^2 + 108*k + 256)*x^4/4! + ...
Square array begins:
     1,     1,     1,     1,     1,     1, ...
     1,     2,     3,     4,     5,     6, ...
     4,     7,    12,    19,    28,    39, ...
    27,    43,    71,   117,   187,   287, ...
   256,   393,   616,   985,  1584,  2521, ...
  3125,  4721,  7197, 11123, 17429, 27525, ...
		

Crossrefs

Columns k=0..2 give A000312, A086331, A277457.
Main diagonal gives A290840.

Programs

  • Mathematica
    Table[Function[k, n!*SeriesCoefficient[Exp[k x]/(1 + LambertW[-x]), {x, 0, n}]][j - n], {j, 0, 10}, {n, 0, j}] // Flatten (* G. C. Greubel, Nov 09 2017 *)

Formula

E.g.f. of column k: exp(k*x)/(1 + LambertW(-x)).
A(n,k) = Sum_{j=0..n} binomial(n,j)*k^(n-j)*j^j. - Fabian Pereyra, Jul 16 2024

A292633 a(n) = n! * [x^n] -exp(n*x)*LambertW(-x).

Original entry on oeis.org

0, 1, 6, 54, 656, 10100, 189252, 4195870, 107803712, 3158565192, 104179336100, 3827097857594, 155176637687568, 6890781261435916, 332846314505306084, 17384125179840159150, 976545328548757184768, 58723524484105985029136, 3764267361608204263229892, 256245748998712921762125922
Offset: 0

Views

Author

Ilya Gutkovskiy, Sep 20 2017

Keywords

Comments

The n-th term of the n-th binomial transform of A000169.

Crossrefs

Main diagonal of A294411.

Programs

  • Mathematica
    Table[n!*SeriesCoefficient[-E^(n*x)*LambertW[-x],{x,0,n}], {n,0,20}] (* Vaclav Kotesovec, Sep 20 2017 *)

Formula

a(n) ~ exp(n*exp(-1)) * n^(n-1) / (1-exp(-1))^(3/2). - Vaclav Kotesovec, Sep 20 2017
Showing 1-3 of 3 results.