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.

A061684 Generalized Bell numbers: column 3 of A275043.

Original entry on oeis.org

1, 1, 5, 64, 1613, 69026, 4566992, 437665649, 57903766797, 10193400044254, 2319001344297830, 665816738235745559, 236563125351122920088, 102303284135845463907107, 53093636013475924370369829, 32666276100771741793923209939, 23573762287735885858839134983437
Offset: 0

Views

Author

N. J. A. Sloane, Jun 18 2001

Keywords

Crossrefs

Probably A061698 from the same paper is an erroneous version of this sequence. - Les Reid, Jan 01 2011
Column k=3 of A275043.
Row sums of A061692.

Programs

  • Maple
    b:= proc(n) option remember; `if`(n=0, 1,
          add(b(n-i)*binomial(n-1, i-1)/i!^2, i=1..n))
        end:
    a:= n-> b(n)*n!^2:
    seq(a(n), n=0..20);  # Alois P. Heinz, May 11 2016
  • Mathematica
    b[n_] := b[n] = If[n==0, 1, Sum[b[n-i]*Binomial[n-1, i-1]/i!^2, {i, 1, n}]];
    a[n_] := b[n]*n!^2;
    Table[a[n], {n, 0, 20}] (* Jean-François Alcover, Mar 14 2017, after Alois P. Heinz *)
  • PARI
    {a(n)=n!^3*polcoeff(exp(sum(m=1, n, x^m/m!^3)+x*O(x^n)), n)} /* Paul D. Hanna, Mar 15 2012 */

Formula

G.f.: Sum_{n>=0} a(n)*x^n/n!^3 = exp( Sum_{n>=1} x^n/n!^3 ). [Paul D. Hanna, Mar 15 2012]
a(0) = 1; a(n) = (1/n) * Sum_{k=0..n-1} binomial(n,k)^3 * (n-k) * a(k). - Ilya Gutkovskiy, Jul 12 2020

Extensions

More terms from Karol A. Penson, Sep 10 2001

A061691 Triangle of generalized Stirling numbers.

Original entry on oeis.org

1, 1, 2, 1, 9, 6, 1, 34, 72, 24, 1, 125, 650, 600, 120, 1, 461, 5400, 10500, 5400, 720, 1, 1715, 43757, 161700, 161700, 52920, 5040, 1, 6434, 353192, 2361016, 4116000, 2493120, 564480, 40320, 1, 24309, 2862330, 33731208, 96960024, 97161120, 39372480, 6531840, 362880
Offset: 1

Views

Author

N. J. A. Sloane, Jun 18 2001

Keywords

Comments

The Eulerian-type number triangle associated with this triangle of generalized Stirling numbers is A192721. The table entry T(n,k) gives the number of uniform block permutations of the set {1,2,...,n} partitioned into k blocks. An example is given below. T(n,k) also gives the number of games of simple patience with n cards resulting in k piles (adapt Algorithm 1.1.22 of Lankham). [Peter Bala, Jul 14 2011]

Examples

			Triangle begins:
  1;
  1,2;
  1,9,6;
  1,34,72,24;
  1,125,650,600,120;
  ...
T(4,2) = 34:
There are 7 partitions of the set {1,2,3,4} into 2 blocks. The four partitions {1,2,3}{4}, {1,2,4}{3}, {1,3,4}{2} and {2,3,4}{1} give rise to 4*4 = 16 uniform block permutations while the remaining 3 partitions {1,2}{3,4}, {1,3}{2,4} and {1,4}{2,3} give 2!*3*3 = 18 uniform block permutations : thus in total there are 16+18 = 34 block permutations between the set partitions of {1,2,3,4} into 2 blocks.
		

Crossrefs

Diagonals give A010763, A061690, A000142, A001809, A061689. Cf. A061692. A023998 (row sums), A192721, A192722.

Programs

  • Maple
    #A061691
    #J = sum {n>=0} z^n/n!^2
    J := BesselJ(0, 2*i*sqrt(z)):
    G := exp(x*(J(z)-1)):
    Gser := simplify(series(G, z = 0, 12)):
    for n from 1 to 10 do
    P[n] := n!^2*sort(coeff(Gser, z, n)) od:
    for n from 1 to 10 do seq(coeff(P[n],x,k), k = 1..n) od;
    # yields sequence in triangular form
    # second Maple program:
    b:= proc(n) option remember; expand(`if`(n=0, 1,
          add(x*b(n-i)*binomial(n, i)/i!, i=1..n)))
        end:
    T:= n-> (p-> seq(coeff(p, x, i)/i!, i=1..n))(b(n)*n!):
    seq(T(n), n=1..12);  # Alois P. Heinz, Sep 10 2019
  • Mathematica
    max = 9; g := Exp[x*(BesselI[0, 2*Sqrt[z]] - 1)]; gser = Series[g, {z, 0, max}, {x, 0, max}]; t[n_, k_] := n!^2*SeriesCoefficient[ gser // Normal, {z, 0, n}, {x, 0, k}]; Flatten[ Table[ t[n, k], {n, 1, max}, {k, 1, n}]] (* Jean-François Alcover, Apr 04 2012, after Maple *)

Formula

T(n, k) = 1/k!*Sum multinomial(n, n_1, n_2, ..n_k)^2, where the sum extends over all compositions (n_1, n_2, .., n_k) of n into exactly k nonnegative parts. - Vladeta Jovovic, Apr 23 2003
From Peter Bala, Jul 14 2011: (Start)
The table entry T(n,k) may also be expressed as a sum over (unordered) partitions of n into k parts:
T(n,k) = sum {partitions m_1*1+...+m_n*n = n, m_1+...+m_n = k} 1/(m_1!*...*m_n!)*{n!/(1!^(m_1)*...*n!^(m_n))}^2.
Generating function:
Let J(z) = sum {n>=0} z^n/n!^2. Then
exp(x*(J(z)-1)) = 1 + x*z + (x + 2*x^2)*z^2/2!^2 + (x + 9*x^2 + 6*x^3)*z^3/3!^2 + ....
Relations with other sequences:
T(n,k) = 1/k!*A192722(n,k).
Row sums [1,3,16,131,...] = A023998. (End)
The row polynomials R(n,x) satisfy the recurrence equation R(n,x) = x*( sum {k = 0..n-1} binomial(n,k)*binomial(n-1,k)*R(k,x) ) with R(0,x) = 1. Also R(n,x + y) = sum {k = 0..n} binomial(n,k)^2*R(k,x)*R(n-k,y). - Peter Bala, Sep 17 2013

Extensions

More terms from Vladeta Jovovic, Apr 23 2003

A061695 Generalized Bell numbers.

Original entry on oeis.org

1, 27, 864, 36000, 1944000, 133358400, 11379916800, 1185137049600, 148142131200000, 21908575180800000, 3785801791242240000, 756127866850836480000, 172901238886557941760000, 44887821634010234880000000, 13132894100921851576320000000, 4301460581188603786297344000000
Offset: 1

Views

Author

N. J. A. Sloane, Jun 19 2001

Keywords

Crossrefs

First subdiagonal of A061692.

Programs

  • Mathematica
    Table[((n+1)!)^2 (n+1) n/8,{n,20}] (* Harvey P. Dale, Jul 25 2024 *)

Formula

a(n) = (n+1)!^2*(n+1)n/8 = A162993(n)*A000217(n). - Oleksandr Kulkov, Oct 10 2022
D-finite with recurrence (-n+1)*a(n) +(n+1)^3*a(n-1)=0. - R. J. Mathar, Jan 17 2025

Extensions

a(8)-a(16) from Alois P. Heinz, Sep 10 2019
Showing 1-3 of 3 results.