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 1-7 of 7 results.

A301419 a(n) = [x^n] Sum_{k>=0} x^k/Product_{j=1..k} (1 - n*j*x).

Original entry on oeis.org

1, 1, 3, 19, 201, 3176, 69823, 2026249, 74565473, 3376695763, 183991725451, 11854772145800, 890415496931689, 77023751991841669, 7592990698770559111, 845240026276785888451, 105409073489605774592897, 14625467507717709778793020, 2244123413703647502288608467, 378751257186051653931253015229
Offset: 0

Views

Author

Ilya Gutkovskiy, Mar 20 2018

Keywords

Crossrefs

Programs

  • GAP
    List([0..20],n->Sum([0..n],k->n^(n-k)*Stirling2(n,k))); # Muniru A Asiru, Mar 20 2018
    
  • Mathematica
    Table[SeriesCoefficient[Sum[x^k/Product[(1 - n j x), {j, 1, k}], {k, 0, n}], {x, 0, n}], {n, 0, 19}]
    Join[{1}, Table[n! SeriesCoefficient[Exp[(Exp[n x] - 1)/n], {x, 0, n}], {n, 19}]]
    Join[{1}, Table[Sum[n^(n - k) StirlingS2[n, k], {k, 0, n}], {n, 19}]]
    (* Or: *)
    A301419[n_] := If[n == 0, 1, n^n BellB[n, 1/n]];
    Table[A301419[n], {n, 0, 19}] (* Peter Luschny, Dec 22 2021 *)
  • PARI
    a(n) = sum(k=0, n, n^(n-k)*stirling(n, k, 2)); \\ Michel Marcus, Mar 23 2018

Formula

a(n) = n! * [x^n] exp((exp(n*x) - 1)/n), for n > 0.
a(n) = Sum_{k=0..n} n^(n-k)*Stirling2(n,k).
a(n) = n^n * BellPolynomial(n, 1/n) for n >= 1. - Peter Luschny, Dec 22 2021
a(n) ~ exp(n/LambertW(n^2) - n) * n^(2*n) / (sqrt(1 + LambertW(n^2)) * LambertW(n^2)^n). - Vaclav Kotesovec, Jun 06 2022

A307066 a(n) = exp(-1) * Sum_{k>=0} (n*k + 1)^n/k!.

Original entry on oeis.org

1, 2, 13, 199, 5329, 216151, 12211597, 909102342, 85761187393, 9957171535975, 1390946372509101, 229587693339867567, 44117901231194922193, 9748599124579281064294, 2451233017637221706477037, 695088863051920283838281851, 220558203335628758134165860609
Offset: 0

Views

Author

Ilya Gutkovskiy, Jun 24 2019

Keywords

Crossrefs

Programs

  • Magma
    A307066:= func< n | (&+[Binomial(n,k)*n^k*Bell(k): k in [0..n]]) >;
    [A307066(n): n in [0..31]]; // G. C. Greubel, Jan 24 2024
    
  • Mathematica
    Table[Exp[-1] Sum[(n k + 1)^n/k!, {k, 0, Infinity}], {n, 0, 16}]
    Table[n! SeriesCoefficient[Exp[Exp[n x] + x - 1], {x, 0, n}], {n, 0, 16}]
    Join[{1}, Table[Sum[Binomial[n, k] n^k BellB[k], {k, 0, n}], {n, 1, 16}]]
  • SageMath
    def A307066(n): return sum(binomial(n,k)*n^k*bell_number(k) for k in range(n+1))
    [A307066(n) for n in range(31)] # G. C. Greubel, Jan 24 2024

Formula

a(n) = n! * [x^n] exp(exp(n*x) + x - 1).
a(n) = Sum_{k=0..n} binomial(n,k) * n^k * Bell(k).

A330605 a(n) = exp(-1) * Sum_{k>=0} (n*k - 1)^n / k!.

Original entry on oeis.org

1, 0, 5, 89, 2737, 121399, 7316101, 572218716, 56142822849, 6731180810945, 965898950508901, 163116461798211503, 31969444766902475185, 7187057932197297484108, 1834860441330563739401765, 527403671798720265634312349, 169396494914472404237224898305
Offset: 0

Views

Author

Ilya Gutkovskiy, Dec 19 2019

Keywords

Crossrefs

Programs

  • Mathematica
    Table[Exp[-1] Sum[(n k - 1)^n/k!, {k, 0, Infinity}], {n, 0, 16}]
    Join[{1}, Table[Sum[(-1)^(n - k) Binomial[n, k] n^k BellB[k], {k, 0, n}], {n, 1, 16}]]
    Table[n! SeriesCoefficient[Exp[Exp[n x] - x - 1], {x, 0, n}], {n, 0, 16}]

Formula

a(n) = n! * [x^n] exp(exp(n*x) - x - 1).
a(n) = Sum_{k=0..n} (-1)^(n - k) * binomial(n,k) * n^k * Bell(k).

A295552 a(n) = n! * [x^n] exp(x*exp(n*x)).

Original entry on oeis.org

1, 1, 5, 46, 689, 15476, 483157, 19719022, 1009495489, 63119450152, 4728073048901, 417482964953594, 42834647403146161, 5043607239173464924, 674409403861210214485, 101517071981284179924526, 17074451852556909059698433, 3187883879639402167714593488, 656838643288782957496595002117
Offset: 0

Views

Author

Ilya Gutkovskiy, Nov 23 2017

Keywords

Crossrefs

Programs

  • Mathematica
    Table[n! SeriesCoefficient[Exp[x Exp[n x]], {x, 0, n}], {n, 0, 18}]
    Join[{1}, Table[Sum[Binomial[n, k] (n k)^(n - k), {k, 0, n}], {n, 1, 18}]]

Formula

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

A292913 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where column k is the expansion of e.g.f. exp(exp(k*x)-1).

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 2, 0, 1, 3, 8, 5, 0, 1, 4, 18, 40, 15, 0, 1, 5, 32, 135, 240, 52, 0, 1, 6, 50, 320, 1215, 1664, 203, 0, 1, 7, 72, 625, 3840, 12636, 12992, 877, 0, 1, 8, 98, 1080, 9375, 53248, 147987, 112256, 4140, 0, 1, 9, 128, 1715, 19440, 162500, 831488, 1917999, 1059840, 21147, 0
Offset: 0

Views

Author

Ilya Gutkovskiy, Sep 26 2017

Keywords

Examples

			E.g.f. of column k: A_k(x) =  1 + k*x/1! + 2*k^2*x^2/2! + 5*k^3*x^3/3! + 15*k^4 x^4/4! + 52*k^5*x^5/5! + ...
Square array begins:
1,   1,     1,      1,      1,       1,  ...
0,   1,     2,      3,      4,       5,  ...
0,   2,     8,     18,     32,      50,  ...
0,   5,    40,    135,    320,     625,  ...
0,  15,   240,   1215,   3840,    9375,  ...
0,  52,  1664,  12636,  53248,  162500,  ...
		

Crossrefs

Columns k=0..3 give A000007, A000110, A055882, A247452.
Rows n=0..2 give A000012, A001477, A001105.
Main diagonal gives A292914.

Programs

  • Maple
    A:= (n, k)-> k^n * combinat[bell](n):
    seq(seq(A(n, d-n), n=0..d), d=0..12);  # Alois P. Heinz, Sep 26 2017
  • Mathematica
    Table[Function[k, n! SeriesCoefficient[Exp[Exp[k x] - 1], {x, 0, n}]][j - n], {j, 0, 10}, {n, 0, j}] // Flatten
    Table[Function[k, SeriesCoefficient[1/(1 + ContinuedFractionK[-((-1)^(i + 1) (i - 1) + i + 3) k x/4, 1, {i, 0, n}]), {x, 0, n}]][j - n], {j, 0, 10}, {n, 0, j}] // Flatten

Formula

O.g.f. of column k: 1/(1 - k*x/(1 - k*x/(1 - k*x/(1 - 2*k*x/(1 - k*x/(1 - 3*k*x/(1 - k*x/(1 - 4*k*x/(1 - ...))))))))), a continued fraction.
E.g.f. of column k: exp(exp(k*x)-1).
A(n,k) = exp(-1)*k^n*Sum_{j>=0} j^n/j!.
A(n,k) = k^n * Bell(n). - Alois P. Heinz, Sep 26 2017

A308330 a(n) = n! * [x^n] exp(exp(n*x)/(1 - x) - 1).

Original entry on oeis.org

1, 2, 19, 346, 10217, 441226, 26023123, 1998840586, 193094418161, 22841006706928, 3239088790361491, 541309430523114804, 105106521730010262745, 23431755937256853296514, 5936989025261397848036755, 1694791457312643753292004446, 540937403928198054978670965089
Offset: 0

Views

Author

Ilya Gutkovskiy, May 20 2019

Keywords

Crossrefs

Programs

  • Mathematica
    Table[n! SeriesCoefficient[Exp[Exp[n x]/(1 - x) - 1], {x, 0, n}], {n, 0, 16}]

A308331 a(n) = n! * [x^n] exp(exp(n*x)/(1 + x) - 1).

Original entry on oeis.org

1, 0, 3, 50, 1449, 61724, 3608515, 275520972, 26505128433, 3125830471928, 442286373458691, 73789189395157730, 14309059313820886681, 3186711239965235356776, 806772967716453793227523, 230153293624841114893344854, 73420355768107554901016231265
Offset: 0

Views

Author

Ilya Gutkovskiy, May 20 2019

Keywords

Crossrefs

Programs

  • Mathematica
    Table[n! SeriesCoefficient[Exp[Exp[n x]/(1 + x) - 1], {x, 0, n}], {n, 0, 16}]
Showing 1-7 of 7 results.