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.

A182988 The number of dominance pairs of integer partitions of n according to either/or dominance order, where dominance between two partitions x and y means that x is majorized by y or y is majorized by x.

Original entry on oeis.org

1, 1, 4, 9, 25, 49, 117, 217, 454, 830, 1594, 2796, 5159, 8777, 15415, 25810, 43819, 71595, 118629, 190148, 307519, 485660, 769382, 1195807, 1864617, 2857630, 4384962, 6641332, 10052272, 15043925, 22501510, 33315580, 49267369, 72250341, 105746966, 153646123
Offset: 0

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Author

Stephen DeSalvo, Feb 06 2011, Feb 13 2011

Keywords

Comments

For two integer partitions of n chosen uniformly at random, a(n)/p(n)^2, where p(n) is the number of partitions of n, is the probability that one dominates the other.
As an example, consider the partitions (4,3,1) and (3,3,2).
4 >= 3, 4+3 >= 3+3, and 4+3+1 = 3+3+2, so we say (4,3,1) majorizes/dominates (3,3,2).
As a non-example, consider (4,1,1,1) and (3,3,1).
4 >= 3, but 4+1 < 3+3, so (4,1,1,1) does NOT dominate (3,3,1).
3 < 4, so (3,3,1) does NOT dominate (4,1,1,1).
Thus the pair (4,1,1,1) and (3,3,1) is not a dominance pair, and does not contribute to a(7).

Examples

			For n=1,2,3,4,5, a(n) = p(n)^2, since these values of n give a linear order for integer partitions.
		

Crossrefs

Programs

  • Maple
    b:= proc(n, m, i, j, t) option remember; `if`(n0,
           b(n, m, i, j-1, true), 0)+b(n, m, i-1, j, false)+
           b(n-i, m-j, min(n-i,i), min(m-j,j), true))))
        end:
    a:= n-> 2*b(n$4, true)-combinat[numbpart](n):
    seq(a(n), n=0..35);  # Alois P. Heinz, Dec 09 2015
  • Mathematica
    b[n_, m_, i_, j_, t_] := b[n, m, i, j, t] = If[n0, b[n, m, i, j-1, True], 0] + b[n, m, i-1, j, False] + b[n-i, m-j, Min[n-i, i], Min[m-j, j], True]]]]; a[n_] := 2*b[n, n, n, n, True] - PartitionsP[n]; Table[a[n], {n, 0, 35}] (* Jean-François Alcover, Dec 09 2016 after Alois P. Heinz *)

Extensions

a(0)=1 prepended by Alois P. Heinz, Jul 07 2015

A248475 Number of pairs of partitions of n that are successors in reverse lexicographic order, but incomparable in dominance (natural, majorization) ordering.

Original entry on oeis.org

0, 0, 0, 0, 0, 2, 3, 4, 6, 9, 12, 17, 22, 30, 39, 51, 65, 85, 107, 136, 171, 216, 268, 335, 413, 512, 629, 772, 941, 1151, 1396, 1694, 2046, 2471, 2969, 3569, 4271, 5110, 6093, 7258, 8620, 10235, 12113, 14325, 16902, 19925, 23434, 27540, 32296, 37842, 44260, 51715, 60322, 70306, 81805
Offset: 1

Views

Author

Wouter Meeussen, Oct 07 2014

Keywords

Comments

Empirical: a(n) is the number of zeros in the subdiagonal of the lower-triangular matrix of coefficients giving the expansion of degree-n complete homogeneous symmetric functions in the Schur basis of the algebra of symmetric functions. - John M. Campbell, Mar 18 2018

Examples

			The successor pair (3,1,1,1) and (2,2,2) are incomparable in dominance ordering, and so are their transposes (4,1,1) and (3,3) and these are the two only pairs for n=6, hence a(6)=2.
		

References

  • Ian G. Macdonald, Symmetric functions and Hall polynomials, Oxford University Press, 1979, pp. 6-8.

Crossrefs

Programs

  • Mathematica
    Needs["Combinatorica`"];
    dominant[par1_?PartitionQ,par2_?PartitionQ]:= Block[{le=Max[Length[par1],Length[par2]],acc},
    acc=Accumulate[PadRight[par1,le]]-Accumulate[PadRight[par2,le]];Which[Min[acc]===0&&Max[acc]>=0,1,Min[acc]<=0&&Max[acc]===0,-1,True,0]];
    Table[Count[Apply[dominant, Partition[Partitions[n], 2,1], 1],0], {n,40}]

A265508 Number of unordered pairs {p,q} of partitions of n into distinct parts such that p and q are incomparable in the dominance order.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 3, 5, 10, 15, 29, 42, 68, 109, 162, 240, 364, 527, 749, 1096, 1529, 2162, 3026, 4179, 5702, 7926, 10650, 14412, 19437, 26042, 34560, 46077, 60617, 79893, 104850, 136851, 177884, 231526, 298868, 385221, 496159, 635725, 812342
Offset: 0

Views

Author

Alois P. Heinz, Dec 09 2015

Keywords

Examples

			a(9) = 1: {621,54}.
a(10) = 1: {721,64}.
a(11) = 3: {821,74}, {821,65}, {731,65}.
a(12) = 5: {6321,543}, {921,84}, {921,75}, {831,75}, {732,651}.
		

Crossrefs

Programs

  • Maple
    b:= proc(n, m, i, j, t) option remember; `if`(n0, b(n, m, i, j-1, true), 0)+
          b(n, m, i-1, j, false)+b(n-i, m-j, max(0, min(n-i, i-1)),
          max(0, min(m-j, j-1)), true))))
        end:
    g:= proc(n, i) option remember; `if`(i*(i+1)/2n, 0, g(n-i, i-1))))
        end:
    a:= n-> (t-> t*(t+1)/2)(g(n$2))-b(n$4, true):
    seq(a(n), n=0..45);
  • Mathematica
    b[n_, m_, i_, j_, t_] := b[n, m, i, j, t] = If[n < m, 0, If[n == 0, 1, If[i < 1, 0, If[t && j > 0, b[n, m, i, j-1, True], 0] + b[n, m, i-1, j, False] + b[n-i, m-j, Max[0, Min[n-i, i-1]], Max[0, Min[m-j, j-1]], True]]]]; g[n_, i_] := g[n, i] = If[i*(i+1)/2 < n, 0, If[n == 0, 1, g[n, i-1] + If[i > n, 0, g[n-i, i-1]]]]; a[n_] := (#*(#+1)/2&)[g[n, n]] - b[n, n, n, n, True]; Table[a[n], {n, 0, 45}] (* Jean-François Alcover, Feb 05 2017, translated from Maple *)

Formula

a(n) = A000217(A000009(n)) - A265506(n).
Showing 1-3 of 3 results.