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.

A104778 Table of values with shape sequence A000041 related to involutions and multinomials. Also column sums of the Kostka matrices associated with the partitions (in Abramowitz & Stegun ordering).

Original entry on oeis.org

1, 1, 1, 2, 1, 2, 4, 1, 2, 3, 5, 10, 1, 2, 3, 5, 7, 13, 26, 1, 2, 3, 4, 5, 8, 11, 14, 20, 38, 76, 1, 2, 3, 4, 5, 8, 10, 13, 14, 23, 32, 42, 60, 116, 232, 1, 2, 3, 4, 5, 5, 8, 11, 14, 17, 14, 24, 30, 40, 56, 43, 73, 103, 136, 196, 382, 764, 1
Offset: 0

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Author

Alford Arnold, Mar 24 2005

Keywords

Comments

Row sums give A178718.

Examples

			The 47 multinomials (corresponding to A005651(4)=47) can be distributed as in the following triangular array:
  1
  9 1
  4 6 1
  9 2 3 1
  1 3 2 3 1
divide each term by
  1
  3 1
  2 3 1
  3 2 3 1
  1 3 2 3 1
yielding
  1
  3 1
  2 2 1
  3 1 1 1
  1 1 1 1 1
with column sums 10 5 3 2 1.
Therefore the fourth row of the table is 1 2 3 5 10
The initial rows are:
  1,
  1,
  1, 2,
  1, 2, 4,
  1, 2, 3, 5, 10,
  1, 2, 3, 5, 7, 13, 26,
  1, 2, 3, 4, 5, 8, 11, 14, 20, 38, 76,
  1, 2, 3, 4, 5, 8, 10, 13, 14, 23, 32, 42, 60, 116, 232,
  1, 2, 3, 4, 5, 5, 8, 11, 14, 17, 14, 24, 30, 40, 56, 43, 73, 103, 136, 196, 382, 764,
  ...
		

Crossrefs

Programs

  • Mathematica
    (* for function 'kostka' see A178718 *)
    aspartitions[n_] := Reverse /@ Sort[Sort /@ Partitions[n]];
    asorder[n_] := rankpartition /@ Reverse /@ Sort[Sort /@ Partitions[n]];
    Flatten[Table[Tr/@ Transpose[PadLeft[#,PartitionsP[k]] [[asorder[k]] ]&/@ kostka/@ aspartitions[k]],{k,11}]]

Extensions

Corrected and edited by Wouter Meeussen, Jan 15 2012

A104779 a(n) is the sum of entries of n-th Kostka matrix for the partitions of n.

Original entry on oeis.org

1, 1, 3, 7, 21, 57, 182, 565, 1931, 6670, 24537, 92337, 364602, 1477148, 6219031, 26875932, 119930947, 548688443, 2580814003, 12425175838, 61302331782, 309055818656, 1592723862598, 8374123173858, 44917765035082, 245452258746785, 1366116578058731, 7736098938006873
Offset: 0

Views

Author

Alford Arnold, Mar 24 2005

Keywords

Comments

a(n) is the number of symmetric nonnegative integer matrices with sum of entries equal to n, no zero rows or columns, and weakly decreasing row and column sums. - Ludovic Schwob, Aug 29 2023

Examples

			For n=4, {1,1,1,1,1} + {0,1,1,2,3} + {0,0,1,1,2} + {0,0,0,1,3} + {0,0,0,0,1} = 21.
		

Crossrefs

Programs

  • Mathematica
    (* See Meeussen link. *)

Formula

Row sums of A104778.

Extensions

a(7) corrected by Alford Arnold, Dec 31 2010
a(8)-a(21) from Amiram Eldar, May 03 2024

A182395 Column sums of an infinite Kostka matrix.

Original entry on oeis.org

1, 2, 3, 5, 4, 8, 14, 5, 11, 14, 24, 43, 6, 14, 20, 34, 44, 78, 142, 7, 17, 26, 44, 30, 65, 114, 85, 150, 271, 499, 8, 20, 32, 54, 40, 86, 150, 100, 130, 228, 408, 302, 544, 996, 1850, 9, 23, 38, 64, 50, 107, 186, 55, 136, 176, 307, 546, 206, 360, 475, 850, 1543, 633, 1139, 2080, 3846, 7193, 10, 26, 44, 74, 60, 128, 222, 70, 172, 222, 386, 684, 190, 286, 498, 654, 1164, 2100, 336, 772, 1376, 1026, 1838, 3336, 6122, 2474, 4514, 8328, 15518, 29186
Offset: 1

Views

Author

Wouter Meeussen, Apr 28 2012

Keywords

Comments

The initial terms of the column sums of Kostka matrices of increasing size converge to a(k). As an infinite sequence, a(k) then equals the k-th column sum of an infinite Kostka matrix.
1,
1, 2,
1, 2, 4,
1, 2, 3, 5, 10,
1, 2, 3, 5, 7, 13, 26,
1, 2, 3, 5, 4, 8, 14, 11, 20, 38, 76
1, 2, 3, 5, 4, 8, 14, 10, 13, 23, 42, 32, 60, 116, 232
1, 2, 3, 5, 4, 8, 14, 5, 11, 14, 24, 43, 17, 30, ..
1, 2, 3, 5, 4, 8, 14, 5, 11, 14, 24, 43, 13, 19, ..
...
For column k, and with mu representing the k-th partition of n, it appears that the number of SSYT with contents equal to partition mu becomes constant for n greater than or equal to 2j+2, with j the value for which A000070(j) < k <= A000070(j+1), when the k-th partition of n becomes (k+i, partition_of_k); i >= 0.

Examples

			a(7)=14 since the 7th partition of n (n >= 5) is (1^5), (3,1^3), (4,1^3), ... converging to (3+i,1^3); i >= 0. The count of SSYT with content (3+i,1^3) or 3+i ones, and a single 2,3 and 4 is limited to the 14 SSYT
{{432111}} {{42111}{3}} {{43111}{2}} {{43211}{1}} {{4211}{31}}
{{4311}{21}} {{4321}{11}} {{4111}{3}{2}} {{4211}{3}{1}} {{4311}{2}{1}}
{{432}{111}} {{421}{31}{1}} {{431}{21}{1}} {{411}{3}{2}{1}}
extended by i ones in the first row.
		

Programs

  • Mathematica
    (* function 'kostka': see A178718 *)
    it=Table[Tr /@ Transpose[ PadLeft[#, PartitionsP[n]] & /@ kostka /@ Partitions[ n ] ], {n, 16}];
    First /@ Cases[ Transpose[{PadRight[Part[ it, -2], PartitionsP[16]], Last[ it ]}], {q_,q_}]

A370723 Number of symmetric (0,1)-matrices with sum of entries equal to n and no zero rows or columns, with weakly decreasing row sums and column sums.

Original entry on oeis.org

1, 2, 5, 14, 39, 123, 393, 1352, 4782, 17824, 68481, 274166
Offset: 1

Views

Author

Ludovic Schwob, May 18 2024

Keywords

Examples

			The a(3) = 5 matrices:
  [1 0 0]  [1 0 0]  [0 1 0]  [0 0 1]  [1 1]
  [0 1 0]  [0 0 1]  [1 0 0]  [0 1 0]  [1 0]
  [0 0 1]  [0 1 0]  [0 0 1]  [1 0 0]
		

Crossrefs

Programs

  • Mathematica
    a[0] = 1;
    a[n_] := a[n] = Length[Select[Subsets[Tuples[Range[n], 2], {n}], Module[{matrix, rows, cols}, matrix = ConstantArray[0, {n, n}]; (matrix[[#[[1]], #[[2]]]] = 1) & /@ #; rows = Total[matrix, {2}]; cols = Total[matrix, {1}]; And[Union[First /@ #] == Range[Max @@ First /@ #], Union[Last /@ #] == Range[Max @@ Last /@ #], Sort[Reverse /@ #] == #, OrderedQ[Reverse[rows]], OrderedQ[Reverse[cols]]]] &]];
    Table[a[n], {n, 1, 6}] (* Robert P. P. McKone, May 19 2024, from Gus Wiseman in A135588 *)
Showing 1-4 of 4 results.