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.

A089515 Triangle of signed numbers used for the computation of the column sequences of triangle A090215.

Original entry on oeis.org

1, -1, 5, 1, -35, 90, -3, 595, -6885, 12005, 143, -150535, 6175845, -39484445, 52245760, -58201, 316465625, -42458934375, 772604284375, -3322503800000, 3547818864576, 216931, -6012846875, 2544269990625, -120371747505625, 1294115230100000, -4145626343257056, 3713894747640000
Offset: 1

Views

Author

Wolfdieter Lang, Dec 01 2003

Keywords

Comments

A090215(n+m,m)= sum(a(m,p)*((p+3)*(p+2)*(p+1)*p)^n,p=1..m)/D(m) with D(m) := A089516(m); m=1,2,..., n>=0.

Examples

			Triangle begins:
   1;
  -1,   5;
   1, -35,   90;
  -3, 595,-6885, 12005;
  ...
A090215(2+3,3) = 199296 = (1*(4*3*2*1)^2 - 35*(5*4*3*2)^2 + 90*(6*5*4*3)^2)/56.
a(3,2)= -35 = 56*(-1)*((5*4*3*2)^2)/((5*4*3*2-4*3*2*1)*(6*5*4*3-5*4*3*2)).
		

Formula

a(n, m)= D(n)*((-1)^(n-m))*(fallfac(m+3, 4)^(n-1))/(product(fallfac(m+3, 4)-fallfac(r+3, 4), r=1..m-1)*product(fallfac(r+3, 4)-fallfac(m+3, 4), r=m+1..n)), with D(n) := A089516(n) and fallfac(n, m) := A008279(n, m) (falling factorials), 1<=m<=n else 0. (Replace in the denominator the first product by 1 if m=1 and the second one by 1 if m=n.)

A089516 Denominators used in A089515 to compute the column sequences of triangle A090215.

Original entry on oeis.org

1, 4, 56, 5712, 18786768, 955776822000, 744550144338000, 187882017072683934000, 114232266380191831872000, 1559289924571192031300084690688000
Offset: 1

Views

Author

Wolfdieter Lang, Dec 01 2003

Keywords

Formula

a(n) = lcm(seq(denominator(a(n, m)), m=1..n)) with the a(n, m) formula given in A089515(n, m) but without the D(n) factor in front and lcm denotes the least common multiple of a set of numbers.

A090214 Generalized Stirling2 array S_{4,4}(n,k).

Original entry on oeis.org

1, 24, 96, 72, 16, 1, 576, 13824, 50688, 59904, 30024, 7200, 856, 48, 1, 13824, 1714176, 21606912, 76317696, 110160576, 78451200, 30645504, 6976512, 953424, 78400, 3760, 96, 1, 331776, 207028224, 8190885888, 74684104704, 253100173824
Offset: 1

Views

Author

Wolfdieter Lang, Dec 01 2003

Keywords

Comments

The row length sequence for this array is [1,5,9,13,17,...] = A016813(n-1), n >= 1.
The g.f. for the k-th column, (with leading zeros and k >= 4) is G(k,x) = x^ceiling(k/4)*P(k,x)/Product_{p = 4..k} (1 - fallfac(p,4)*x), with fallfac(n,m) := A008279(n,m) (falling factorials) and P(k,x) := Sum_{m = 0..kmax(k)} A090221(k,m)*x^m, k >= 4, with kmax(k) := A057353(k-4)= floor(3*(k-4)/4). For the recurrence of the G(k,x) see A090221.
Codara et al., show that T(n,k) gives the number of k-colorings of the graph nK_4 (the disjoint union of n copies of the complete graph K_4). - Peter Bala, Aug 15 2013

Examples

			Table begins
n\k|   4      5      6      7      8     9   10   11   12
= = = = = = = = = = = = = = = = = = = = = = = = = = = = =
1  |   1
2  |  24     96     72     16      1
3  | 576  13824  50688  59904  30024  7200  856   48    1
...
		

Crossrefs

Cf. A090215, A071379 (row sums), A090213 (alternating row sums).
S_{1, 1} = A008277, S_{2, 1} = A008297 (ignoring signs), S_{3, 1} = A035342, S_{2, 2} = A078739, S_{3, 2} = A078740, S_{3, 3} = A078741.

Programs

  • Maple
    T:= (n,k) -> (-1)^k/k!*add((-1)^p*binomial(k,p)*(p*(p-1)*(p-2)*(p-3))^n,p=4..k):
    seq(seq(T(n,k),k=4..4*n),n=1..10); # Robert Israel, Jan 28 2016
  • Mathematica
    a[n_, k_] := (((-1)^k)/k!)*Sum[((-1)^p)*Binomial[k, p]*FactorialPower[p, 4]^n, {p, 4, k}]; Table[a[n, k], {n, 1, 5}, {k, 4, 4*n}] // Flatten (* Jean-François Alcover, Sep 05 2012, updated Jan 28 2016 *)

Formula

a(n, k) = (-1)^k/k! * Sum_{p = 4..k} (-1)^p * binomial(k, p) * fallfac(p, 4)^n, with fallfac(p, 4) := A008279(p, 4) = p*(p - 1)*(p - 2)*(p - 3); 4 <= k <= 4*n, n >= 1, else 0. From eq.(19) with r = 4 of the Blasiak et al. reference.
E^n = Sum_{k = 4..4*n} a(n,k)*x^k*D^k where D is the operator d/dx, and E the operator (x^4)*d^4/dx^4.
The row polynomials R(n,x) are given by the Dobinski-type formula R(n,x) = exp(-x)*Sum_{k >= 0} (k*(k - 1)*(k - 2)*(k - 3))^n*x^k/k!. - Peter Bala, Aug 15 2013

A090217 A generalization of triangle A071951 (Legendre-Stirling).

Original entry on oeis.org

1, 120, 1, 14400, 840, 1, 1728000, 619200, 3360, 1, 207360000, 447552000, 9086400, 10080, 1, 24883200000, 322444800000, 23345280000, 76824000, 25200, 1, 2985984000000, 232185139200000, 59152550400000, 539602560000, 457848000
Offset: 1

Views

Author

Wolfdieter Lang, Dec 01 2003

Keywords

Comments

This is the fourth member of the family A071951 (Legendre-Stirling,(2,2) case), A089504((3,3)-case), A090215 ((4,4)-case).
This triangle underlies the array entry A090216 ((5,5)-generalized Stirling2).

Examples

			Triangle starts:
[1];
[120,1];
[14400,840,1];
[1728000,619200,3360,1];
...
		

Crossrefs

The column sequences (without leading zeros) are powers of 120, etc.

Programs

  • Mathematica
    max = 10; f[m_] := 1/Product[1 - FactorialPower[r + 4, 5]*x, {r, 1, m}]; col[m_] := CoefficientList[f[m] + O[x]^(max - m + 1), x]; a[n_, m_] := col[m][[n - m + 1]]; Table[a[n, m], {n, 1, max}, {m, 1, n}] // Flatten (* Jean-François Alcover, Sep 02 2016 *)

Formula

G.f. for m-th column (without leading zeros and m>=1) is 1/product(1-fallfac(r+4, 5)*x, r=1..m) with fallfac(n, k) := A008279(n, k) (falling factorials).
a(n, m)=sum(A090435(m, p)*fallfac(p, 5)^(n-m), p=1..m)/D(m) if n>=m>=1 else 0; with D(m) := A090436(m).
Showing 1-4 of 4 results.