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.

A008300 Triangle read by rows: T(n,k) (n >= 0, 0 <= k <= n) gives number of {0,1} n X n matrices with all row and column sums equal to k.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 6, 6, 1, 1, 24, 90, 24, 1, 1, 120, 2040, 2040, 120, 1, 1, 720, 67950, 297200, 67950, 720, 1, 1, 5040, 3110940, 68938800, 68938800, 3110940, 5040, 1, 1, 40320, 187530840, 24046189440, 116963796250, 24046189440, 187530840, 40320, 1, 1, 362880, 14398171200, 12025780892160, 315031400802720, 315031400802720, 12025780892160, 14398171200, 362880, 1
Offset: 0

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Author

Keywords

Comments

Or, triangle of multipermutation numbers T(n,k), n >= 0, 0 <= k <= n: number of relations on an n-set such that all vertical sections and all horizontal sections have k elements.

Examples

			Triangle begins:
  1;
  1,    1;
  1,    2,       1;
  1,    6,       6,        1;
  1,   24,      90,       24,        1;
  1,  120,    2040,     2040,      120,       1;
  1,  720,   67950,   297200,    67950,     720,    1;
  1, 5040, 3110940, 68938800, 68938800, 3110940, 5040, 1;
  ...
		

References

  • L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 236, P(n,k).

Crossrefs

Row sums give A067209.
Central coefficients are A058527.
Cf. A000142 (column 1), A001499 (column 2), A001501 (column 3), A058528 (column 4), A075754 (column 5), A172544 (column 6), A172541 (column 7), A172536 (column 8), A172540 (column 9), A172535 (column 11), A172534 (column 12), A172538 (column 13), A172537 (column 14).
Cf. A133687, A333157 (symmetric matrices), A257493 (nonnegative elements), A260340 (up to row permutations), A364068 (traceless).

Programs

  • PARI
    T(n, k)={
      local(M=Map(Mat([n, 1])));
      my(acc(p, v)=my(z); mapput(M, p, if(mapisdefined(M, p, &z), z+v, v)));
      my(recurse(i, p, v, e) = if(i<0, if(!e, acc(p, v)), my(t=polcoef(p,i)); for(j=0, min(t, e), self()(i-1, p+j*(x-1)*x^i, binomial(t, j)*v, e-j))));
      for(r=1, n, my(src=Mat(M)); M=Map(); for(i=1, matsize(src)[1], recurse(k-1, src[i, 1], src[i, 2], k))); vecsum(Mat(M)[,2]);
    } \\ Andrew Howroyd, Apr 03 2020

Formula

Comtet quotes Everett and Stein as showing that T(n,k) ~ (kn)!(k!)^(-2n) exp( -(k-1)^2/2 ) for fixed k as n -> oo.
T(n,k) = T(n,n-k).

Extensions

More terms from Greg Kuperberg, Feb 08 2001

A202784 T(n,k) is the number of n X n 0..k arrays with row and column sums equal.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 3, 4, 1, 1, 4, 9, 14, 1, 1, 5, 16, 87, 140, 1, 1, 6, 25, 340, 5673, 4322, 1, 1, 7, 36, 1001, 89520, 2577513, 434542, 1, 1, 8, 49, 2442, 790425, 290838284, 8459809773, 144109562, 1, 1, 9, 64, 5215, 4756140, 11991502235, 12092687195284, 207495141083975, 165431317452, 1
Offset: 0

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Author

R. H. Hardin, Dec 24 2011

Keywords

Examples

			Table starts
n\k | 0            1               2              3                4
----+-------------------------------------------------------------------
  0 | 1            1               1              1                1 ...
  1 | 1            2               3              4                5 ...
  2 | 1            4               9             16               25 ...
  3 | 1           14              87            340             1001 ...
  4 | 1          140            5673          89520           790425 ...
  5 | 1         4322         2577513      290838284      11991502235 ...
  6 | 1       434542      8459809773 12092687195284 3632894572698505 ...
  7 | 1    144109562 207495141083975 ...
  8 | 1 165431317452 ...
  ...
Some solutions for n=4 k=3
..3..1..2..1....2..2..0..3....1..1..1..2....1..3..0..0....1..2..0..2
..2..3..2..0....1..2..2..2....3..0..1..1....1..0..1..2....3..1..0..1
..2..2..0..3....3..0..3..1....0..3..2..0....2..0..1..1....0..0..3..2
..0..1..3..3....1..3..2..1....1..1..1..2....0..1..2..1....1..2..2..0
		

Crossrefs

Extensions

Added crossrefs. - R. H. Hardin, Jan 05 2012
Row and column zero inserted by Andrew Howroyd, Oct 14 2024

A181236 T(n,k)=Number of (k*n)Xn binary matrices with all row sums equal and all column sums equal.

Original entry on oeis.org

2, 2, 4, 2, 8, 14, 2, 22, 182, 140, 2, 72, 3362, 49772, 4322, 2, 254, 69302, 33235358, 113400002, 434542, 2, 926, 1513514, 27896484332, 5210265060002, 4027811102702, 144109562, 2, 3434, 34306274, 26012734507190, 298289608088472002
Offset: 1

Views

Author

R. H. Hardin Oct 10 2010

Keywords

Comments

Table starts
............2...................2....................2..................2
............4...................8...................22.................72
...........14.................182.................3362..............69302
..........140...............49772.............33235358........27896484332
.........4322...........113400002........5210265060002.298289608088472002
.......434542.......4027811102702.90698868503010138802...................
....144109562.1237505791330809002........................................
.165431317452............................................................

Examples

			All solutions for 6X2
..0..0....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1
..0..0....0..1....0..1....0..1....0..1....1..0....1..0....1..0....1..0....1..0
..0..0....0..1....1..0....1..0....1..0....0..1....0..1....0..1....1..0....1..0
..0..0....1..0....0..1....1..0....1..0....0..1....1..0....1..0....0..1....0..1
..0..0....1..0....1..0....1..0....0..1....1..0....1..0....0..1....1..0....0..1
..0..0....1..0....1..0....0..1....1..0....1..0....0..1....1..0....0..1....1..0
...
..0..1....1..0....1..0....1..0....1..0....1..0....1..0....1..0....1..0....1..0
..1..0....0..1....0..1....0..1....0..1....0..1....0..1....1..0....1..0....1..0
..1..0....0..1....0..1....0..1....1..0....1..0....1..0....0..1....0..1....0..1
..1..0....0..1....1..0....1..0....0..1....0..1....1..0....0..1....0..1....1..0
..0..1....1..0....1..0....0..1....1..0....0..1....0..1....1..0....0..1....0..1
..0..1....1..0....0..1....1..0....0..1....1..0....0..1....0..1....1..0....0..1
...
..1..0....1..1
..1..0....1..1
..1..0....1..1
..0..1....1..1
..0..1....1..1
..0..1....1..1
		

Crossrefs

Column 1 is A067209
Row 2 is twice A112849

A333681 Number of non-isomorphic n X n binary matrices with all row and column sums equal up to permutation of rows and columns.

Original entry on oeis.org

1, 2, 3, 4, 6, 8, 19, 44, 314, 7526, 846993, 324127860, 403254094632, 1555631972009430, 19731915624463099553, 791773335030637885025288, 107432353216118868234728540268, 47049030539260648478475949282317452, 71364337698829887974206671525372672234855
Offset: 0

Views

Author

Andrew Howroyd, Apr 01 2020

Keywords

Examples

			The a(2) = 3 matrices are:
  [0 0]  [0 1]  [1 1]
  [0 0]  [1 0]  [1 1]
		

Crossrefs

Row sums of A133687.

Formula

a(n) = A000519(n) + 1.
Showing 1-4 of 4 results.