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.

Previous Showing 21-27 of 27 results.

A003439 Number of 6 X 6 stochastic matrices of integers: all rows and columns sum to n.

Original entry on oeis.org

1, 720, 202410, 20933840, 1047649905, 30767936616, 602351808741, 8575979362560, 94459713879600, 842286559093240, 6292583664553881, 40447642842118656, 228438173705550566, 1152877640765297760, 5271278793334883190, 22085628572718605376, 85604721304213863531
Offset: 0

Views

Author

Keywords

References

  • Matthias Beck and Dennis Pixton, The Ehrhart Polynomial of the Birkhoff Polytope, Discrete & Computational Geometry, 30(4)(2003), 623-637.
  • D. M. Jackson and G. H. J. van Rees, The enumeration of generalized double stochastic nonnegative integer square matrices, SIAM J. Comput., 4 (1975), 474-477.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Row n=6 of A257493.
Cf. A005467.

Formula

a(n) = Sum_{j=0..10} A005467(j) * binomial(5+j+n, 5+2*j). - Andrew Howroyd, Apr 09 2020

Extensions

More terms from Melissa Erdmann (merdmann(AT)nebrwesleyan.edu), May 07 2009
Offset changed to 0 by Alois P. Heinz, Apr 26 2015
Name clarified by Charles R Greathouse IV, Mar 03 2018

A172806 Number of n X n of nonnegative integers with all row and column sums equal to 4.

Original entry on oeis.org

1, 1, 5, 120, 10147, 2224955, 1047649905, 936670590450, 1455918295922650, 3680232136895819610, 14356628851597700179050, 82857993930808028192521800, 683327637694741065563262206250, 7821620120684573354895941635688250
Offset: 0

Views

Author

R. H. Hardin, Feb 06 2010

Keywords

Crossrefs

A323523 Number of positive integer square matrices with entries summing to n and equal row and column sums.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 3, 1, 4, 2, 5, 1, 12, 1, 7, 22, 9, 1, 64, 1, 34, 121, 11, 1, 525, 2, 13, 407, 2022, 1, 801, 1, 10163, 1036, 17, 6211, 41735, 1, 19, 2212, 285784, 1, 3822, 1, 381446, 2229142, 23, 1, 1189540, 2, 22069276, 7261, 2309410, 1, 20943183, 164176641
Offset: 0

Views

Author

Gus Wiseman, Jan 17 2019

Keywords

Comments

Also the number of non-normal semi-magic squares with positive integer entries summing to n.

Examples

			The a(12) = 12 matrices:
  [12]
.
  [1 5] [5 1] [2 4] [4 2] [3 3]
  [5 1] [1 5] [4 2] [2 4] [3 3]
.
  [1 1 2] [1 1 2] [1 2 1] [1 2 1] [2 1 1] [2 1 1]
  [1 2 1] [2 1 1] [1 1 2] [2 1 1] [1 1 2] [1 2 1]
  [2 1 1] [1 2 1] [2 1 1] [1 1 2] [1 2 1] [1 1 2]
		

Crossrefs

Programs

  • Mathematica
    primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];
    facs[n_]:=If[n<=1,{{}},Join@@Table[Map[Prepend[#,d]&,Select[facs[n/d],Min@@#>=d&]],{d,Rest[Divisors[n]]}]];
    ptnsqrs[n_]:=Union@@Permutations/@Select[Union@@(Tuples[Permutations/@#]&/@Map[primeMS,facs[n],{2}]),And[SameQ@@Length/@#,Length[#]==0||Length[#]==Length[First[#]]]&];
    Table[Sum[Length[Select[ptnsqrs[Times@@Prime/@y],And[SameQ@@Total/@#,SameQ@@Total/@Transpose[#]]&]],{y,IntegerPartitions[n]}],{n,10}]

Formula

a(p) = 1 and a(p^2) = 2 for p prime (see comment in A323349). - Chai Wah Wu, Jan 20 2019
a(n) = Sum_{d|n, d<=n/d} A257493(d, n/d-d) for n > 0. - Andrew Howroyd, Apr 10 2020

Extensions

a(16)-a(55) from Chai Wah Wu, Jan 20 2019

A008552 Number of 7 X 7 stochastic matrices of integers.

Original entry on oeis.org

1, 5040, 9135630, 4662857360, 936670590450, 94161778046406, 5562418293759978, 215717608046511873, 5945968652327831925, 123538613356253145400, 2023270039486328373811, 27046306550096288483238, 303378141987182515342992, 2920054336492521720572276
Offset: 0

Views

Author

John Mount (jmount(AT)msri.org)

Keywords

Crossrefs

Row n=7 of A257493.

Extensions

Offset changed to 0 by Alois P. Heinz, Apr 26 2015

A160318 Number of 8 X 8 stochastic matrices of integers.

Original entry on oeis.org

1, 40320, 545007960, 1579060246400, 1455918295922650, 569304690994400256, 114601242382721619224, 13590707419428422843904, 1046591482728407939338275, 56272722406349235035916800, 2233160342369825596702148720, 68316292103293669997188919040
Offset: 0

Views

Author

Melissa Erdmann (merdmann(AT)nebrwesleyan.edu), May 08 2009

Keywords

References

  • Matthias Beck and Dennis Pixton, The Ehrhart Polynomial of the Birkhoff Polytope, Discrete & Computational Geometry, 30(4)(2003), 623-637.

Crossrefs

Row n=8 of A257493.

A160319 Number of 9 X 9 stochastic matrices of integers.

Original entry on oeis.org

1, 362880, 41514583320, 772200774683520, 3680232136895819610, 6274236760589024662176, 4801114002903931560293544, 1933216160887575268614599040, 459761347800901006933211075259, 70417932475495769964322670258947, 7424168163091445250817494013145952
Offset: 0

Views

Author

Melissa Erdmann (merdmann(AT)nebrwesleyan.edu), May 08 2009

Keywords

References

  • Matthias Beck and Dennis Pixton, The Ehrhart Polynomial of the Birkhoff Polytope, Discrete & Computational Geometry, 30(4)(2003), 623-637.

Crossrefs

Row n=9 of A257493.

A259473 Irregular triangle read by rows of coefficients arising in the enumeration of doubly stochastic matrices of integers, n >= 1, 0 <= k <= (n-1)*(n-2).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 14, 87, 148, 87, 14, 1, 1, 103, 4306, 63110, 388615, 1115068, 1575669, 1115068, 388615, 63110, 4306, 103, 1, 1, 694, 184015, 15902580, 567296265, 9816969306, 91422589980, 490333468494, 1583419977390, 3166404385990, 3982599815746, 3166404385990
Offset: 1

Views

Author

N. J. A. Sloane, Jul 03 2015

Keywords

Comments

The n-th row of A257493 is a polynomial of degree (n-1)^2. This triangle gives the coefficients of the numerator of the generating functions for A257493 with denominators being (1-x)^(1+(n-1)^2). - Andrew Howroyd, Apr 11 2020

Examples

			Triangle begins:
  1;
  1;
  1,1,1;
  1,14,87,148,87,14,1;
  1,103,4306,63110,388615,1115068,1575669,1115068,388615,63110,4306,103,1;
  ...
		

Crossrefs

Row sums are A037302.

Formula

T(n,k) = Sum_{i=0..k} A257493(n, k-i)*(-1)^i*binomial(1+(n-1)^2,i). - Andrew Howroyd, Apr 11 2020

Extensions

a(1)=1 prepended and terms a(26) and beyond from Andrew Howroyd, Apr 11 2020
Previous Showing 21-27 of 27 results.