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.

A318183 a(n) = [x^n] Sum_{k>=0} x^k/Product_{j=1..k} (1 + n*j*x).

Original entry on oeis.org

1, 1, -1, 1, 25, -674, 15211, -331827, 5987745, 15901597, -13125035449, 1292056076070, -103145930581319, 7462324963409941, -464957409070517453, 16313974895147212801, 2059903411953959582849, -708700955022151333496910, 143215213612865558214820303, -24681846509158429152517973103
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 20 2018

Keywords

Crossrefs

Programs

  • 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[(1 - Exp[-n x])/n], {x, 0, n}], {n, 19}]]
    Join[{1}, Table[Sum[(-n)^(n - k) StirlingS2[n, k], {k, n}], {n, 19}]]
    Join[{1}, Table[(-n)^n BellB[n, -1/n], {n, 1, 21}]] (* Peter Luschny, Aug 20 2018 *)
  • PARI
    {a(n) = sum(k=0, n, (-n)^(n-k)*stirling(n, k, 2))} \\ Seiichi Manyama, Jul 27 2019

Formula

a(n) = n! * [x^n] exp((1 - exp(-n*x))/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, Aug 20 2018

A350260 Triangle read by rows. T(n, k) = k^n * BellPolynomial(n, 1/k) for k > 0, if k = 0 then T(n, k) = k^n.

Original entry on oeis.org

1, 0, 1, 0, 2, 3, 0, 5, 11, 19, 0, 15, 49, 109, 201, 0, 52, 257, 742, 1657, 3176, 0, 203, 1539, 5815, 15821, 35451, 69823, 0, 877, 10299, 51193, 170389, 447981, 1007407, 2026249, 0, 4140, 75905, 498118, 2032785, 6282416, 16157905, 36458010, 74565473
Offset: 0

Views

Author

Peter Luschny, Dec 22 2021

Keywords

Examples

			Triangle starts:
[0] 1
[1] 0,    1
[2] 0,    2,     3
[3] 0,    5,    11,     19
[4] 0,   15,    49,    109,     201
[5] 0,   52,   257,    742,    1657,    3176
[6] 0,  203,  1539,   5815,   15821,   35451,    69823
[7] 0,  877, 10299,  51193,  170389,  447981,  1007407,  2026249
[8] 0, 4140, 75905, 498118, 2032785, 6282416, 16157905, 36458010, 74565473
		

Crossrefs

Programs

  • Maple
    A350260 := (n, k) -> ifelse(k = 0, k^n, k^n * BellB(n, 1/k)):
    seq(seq(A350260(n, k), k = 0..n), n = 0..8);
  • Mathematica
    T[n_, k_] := If[k == 0, k^n, k^n BellB[n, 1/k]];
    Table[T[n, k], {n, 0, 8}, {k, 0, n}] // Flatten

A337043 a(0) = 1; thereafter a(n) = exp(-1/n) * Sum_{k>=0} (n*k - 1)^n / (n^k * k!).

Original entry on oeis.org

1, 0, 2, 9, 112, 1875, 43416, 1310946, 49778688, 2313362673, 128894500000, 8469572721533, 647341071298560, 56871349337125648, 5684260661585401728, 640631299771142578125, 80788871646072851660800, 11323828537291632967145015, 1753760620207362607774290432
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 12 2020

Keywords

Crossrefs

Programs

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

Formula

a(n) = [x^n] (1/(1 + x)) * Sum_{k>=0} (x/(1 + x))^k / Product_{j=1..k} (1 - n*j*x/(1 + x)).
a(n) = n! * [x^n] exp((exp(n*x) - 1) / n - x), for n > 0.
a(n) = Sum_{k=0..n} (-1)^(n-k) * binomial(n,k) * n^k * BellPolynomial_k(1/n), for n > 0.

A334162 a(0) = 1; thereafter a(n) = exp(-1/n) * Sum_{k>=0} (n*k + 1)^n / (n^k * k!).

Original entry on oeis.org

1, 2, 6, 35, 352, 5307, 111592, 3117900, 111259904, 4912490375, 261954304224, 16560019685937, 1222893826048000, 104189533522270666, 10132262911996769408, 1114216450970154278543, 137427598621356912082944, 18877351974681584403701519, 2869969478954093766868948480
Offset: 0

Views

Author

Ilya Gutkovskiy, Apr 16 2020

Keywords

Crossrefs

Programs

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

Formula

a(n) = [x^n] (1/(1 - x)) * Sum_{k>=0} (x/(1 - x))^k / Product_{j=1..k} (1 - n*j*x/(1 - x)).
a(n) = n! * [x^n] exp(x + (exp(n*x) - 1) / n), for n > 0.
a(n) = A334165(n,n).

A331690 a(n) = Sum_{k=0..n} Stirling2(n,k) * k! * n^(n - k).

Original entry on oeis.org

1, 1, 4, 33, 456, 9445, 272448, 10386817, 503758720, 30202999821, 2189000524800, 188349613075393, 18954958449853440, 2203304642871358741, 292675996808408743936, 44022321302156791898625, 7438113993194856900034560, 1401876939543892434209075581
Offset: 0

Views

Author

Ilya Gutkovskiy, Jan 24 2020

Keywords

Crossrefs

Programs

  • Mathematica
    Join[{1}, Table[Sum[StirlingS2[n, k] k! n^(n - k), {k, 0, n}], {n, 1, 17}]]
    Table[SeriesCoefficient[Sum[k! x^k/Product[(1 - n j x), {j, 1, k}], {k, 0, n}], {x, 0, n}], {n, 0, 17}]
    Join[{1}, Table[n^(n + 1) PolyLog[-n, 1/(n + 1)]/(n + 1), {n, 1, 17}]]
  • PARI
    a(n) = sum(k=0, n, stirling(n, k, 2)*k!*n^(n-k)); \\ Michel Marcus, Jan 24 2020

Formula

a(n) = [x^n] Sum_{k>=0} k! * x^k / Product_{j=1..k} (1 - n*j*x).
a(n) = n! * [x^n] n / (1 + n - exp(n*x)) for n > 0.
a(n) = n^(n + 1) * Sum_{k>=1} k^n / (n + 1)^(k + 1) for n > 0.
a(n) ~ n! * n^(n+1) / ((n+1) * log(n+1)^(n+1)). - Vaclav Kotesovec, Jun 06 2022

A309401 a(n) = A306245(n,n).

Original entry on oeis.org

1, 1, 3, 43, 5949, 12950796, 586826390263, 669793946192984257, 22558227235537152753501561, 25741074696455818592335996518315259, 1124843928218943684789052411802502269971863691, 2100464404490451025972467064515428575200326254804659324780
Offset: 0

Views

Author

Seiichi Manyama, Jul 28 2019

Keywords

Crossrefs

Main diagonal of A306245.

Programs

  • Maple
    b:= proc(n, k) option remember; `if`(n=0, 1,
          add(k^j*binomial(n-1, j)*b(j, k), j=0..n-1))
        end:
    a:= n-> b(n$2):
    seq(a(n), n=0..12);  # Alois P. Heinz, Jul 28 2019
  • Mathematica
    b[0, _] = 1;
    b[n_, k_] := b[n, k] = Sum[k^j Binomial[n-1, j] b[j, k], {j, 0, n-1}];
    a[n_] := b[n, n];
    a /@ Range[0, 12] (* Jean-François Alcover, Nov 14 2020, after Alois P. Heinz *)
  • Ruby
    def ncr(n, r)
      return 1 if r == 0
      (n - r + 1..n).inject(:*) / (1..r).inject(:*)
    end
    def A(k, n)
      ary = [1]
      (1..n).each{|i| ary << (0..i - 1).inject(0){|s, j| s + k ** j * ncr(i - 1, j) * ary[j]}}
      ary
    end
    def A309401(n)
      (0..n).map{|i| A(i, i)}
    end
    p A309401(20)
Showing 1-6 of 6 results.