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.

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A173403 Inverse binomial transform of A002416.

Original entry on oeis.org

1, 1, 13, 469, 63577, 33231721, 68519123173, 562469619451069, 18442242396353040817, 2417685638793025070212561, 1267626422541873052658376446653, 2658442047546208031914776455678477989, 22300713297142388711251601783864453690641417
Offset: 0

Views

Author

Brian Drake, Feb 17 2010

Keywords

Comments

a(n) is the number of n X n matrices of 0's and 1's with the property that there is no index k such that both the k-th column and the k-th row consist of all zeros.
a(n) is the number of binary relations on n labeled vertices with no vertex of indegree and outdegree = 0. - Geoffrey Critzer, Oct 02 2012

References

  • E. A. Bender and S. G. Williamson, Foundations of Combinatorics with Applications, Dover, 2005, exercise 4.1.6.

Crossrefs

Programs

  • Maple
    N:=8: seq( sum(binomial(n,i)*2^((n-i)^2)*(-1)^(i), i=0..n), n=0..N);
  • Mathematica
    Table[Sum[(-1)^k Binomial[n,k] 2^(n-k)^2,{k,0,n}],{n,0,20}]  (* Geoffrey Critzer, Oct 02 2012 *)

Formula

a(n) = Sum_{k=0..n} (-1)^k*binomial(n,k)*2^((n-k)^2).
a(n) ~ 2^(n^2). - Vaclav Kotesovec, Oct 30 2017

A321615 Triangle read by rows: T(n,k) is the number of k X k integer matrices with sum of elements n, with no zero rows or columns, up to row and column permutation.

Original entry on oeis.org

1, 0, 1, 0, 1, 1, 0, 1, 2, 1, 0, 1, 6, 3, 1, 0, 1, 9, 13, 3, 1, 0, 1, 17, 38, 20, 3, 1, 0, 1, 23, 97, 82, 23, 3, 1, 0, 1, 36, 217, 311, 126, 24, 3, 1, 0, 1, 46, 453, 968, 624, 151, 24, 3, 1, 0, 1, 65, 868, 2825, 2637, 933, 162, 24, 3, 1, 0, 1, 80, 1585, 7394, 10098, 4942, 1132, 165, 24, 3, 1
Offset: 0

Views

Author

Andrew Howroyd, Nov 14 2018

Keywords

Comments

Also the number of non-isomorphic multiset partitions of weight n with k parts and k vertices, where the weight of a multiset partition is the sum of sizes of its parts. - Gus Wiseman, Nov 18 2018

Examples

			Triangle begins:
    1
    0  1
    0  1    1
    0  1    2    1
    0  1    6    3    1
    0  1    9   13    3    1
    0  1   17   38   20    3    1
    0  1   23   97   82   23    3    1
    0  1   36  217  311  126   24    3    1
    0  1   46  453  968  624  151   24    3    1
    0  1   65  868 2825 2637  933  162   24    3    1
		

Crossrefs

Programs

  • Mathematica
    (* See A318795 for M[m, n, k]. *)
    T[n_, k_] := M[k, k, n] - 2 M[k, k-1, n] + M[k-1, k-1, n];
    Table[T[n, k], {n, 1, 11}, {k, 1, n}] // Flatten (* Jean-François Alcover, Nov 24 2018, from PARI *)
  • PARI
    \\ See A318795 for M.
    T(n, k) = if(k==0, n==0, M(k, k, n) - 2*M(k, k-1, n) + M(k-1, k-1, n));
    
  • PARI
    \\ See A340652 for G.
    T(n)={[Vecrev(p) | p<-Vec(1 + sum(k=1, n, y^k*(polcoef(G(k, n, n, y), k, y) - polcoef(G(k-1, n, n, y), k, y))))]}
    { my(A=T(10)); for(i=1, #A, print(A[i])) } \\ Andrew Howroyd, Jan 16 2024

Extensions

Column k=0 inserted by Andrew Howroyd, Jan 17 2024

A055082 Number of 4 X n binary matrices with no zero rows or columns, up to row and column permutation.

Original entry on oeis.org

1, 8, 42, 179, 633, 2001, 5745, 15274, 38000, 89331, 199715, 427184, 878152, 1741964, 3345562, 6239390, 11327863, 20065972, 34747460, 58924066, 98002370, 160086580, 257148244, 406637336, 633669040, 973971441, 1477810227, 2215179768, 3282598034, 4811946882
Offset: 1

Views

Author

Vladeta Jovovic, Jun 13 2000

Keywords

Crossrefs

Column k=4 of A056152.

Programs

Extensions

Terms a(21) and beyond from Andrew Howroyd, Mar 25 2020

A055083 Number of 5 X n binary matrices with no zero rows or columns, up to row and column permutation.

Original entry on oeis.org

1, 11, 91, 633, 3835, 20755, 102089, 461272, 1930310, 7534742, 27602968, 95428291, 312864361, 976985630, 2917175450, 8357692894, 23046527311, 61337188725, 157950527167, 394427897066, 957058104818, 2260601179661, 5206447640059, 11709619965923, 25752660738209
Offset: 1

Views

Author

Vladeta Jovovic, Jun 13 2000

Keywords

Crossrefs

Column k=5 of A056152.

Programs

Extensions

Terms a(21) and beyond from Andrew Howroyd, Mar 25 2020

A283500 Triangle read by rows: T(n,k) = number of n X n (0,1) matrices with at most k 1's in each row or column.

Original entry on oeis.org

2, 7, 16, 34, 265, 512, 209, 7343, 41503, 65536, 1546, 304186, 6474726, 24997921, 33554432, 13327, 17525812, 1709852332, 21252557377, 57366997447, 68719476736, 130922, 1336221251, 702998475376, 34215495252681, 252540841305558, 505874809287625
Offset: 1

Views

Author

R. J. Mathar, Mar 09 2017

Keywords

Examples

			Triangle begins:
2;
7,     16;
34,    265,      512;
209,   7343,     41503,      65536;
1546,  304186,   6474726,    24997921,    33554432;
13327, 17525812, 1709852332, 21252557377, 57366997447, 68719476736;
...
		

Crossrefs

Cf. A002720 (column k=1), A197458 (column k=2), A008300 (exactly k 1s).
Main diagonal and first lower diagonal give: A002416, A048291.
Cf. A247158 (k=n/2).

A116507 Number of singular n X n rational {0,1}-matrices with no zero rows or columns.

Original entry on oeis.org

0, 1, 91, 18943, 12483601, 28530385447, 235529139302185, 7183142489571818623
Offset: 1

Views

Author

Vladeta Jovovic, Apr 03 2006

Keywords

Crossrefs

Formula

a(n) = A048291(n) - A055165(n).

A230879 Number of 2-packed n X n matrices.

Original entry on oeis.org

1, 2, 56, 16064, 39156608, 813732073472, 147662286695991296, 237776857718965784182784, 3425329990022686416530808209408, 443021337239562368918979788606843912192, 515203019085226443540506018909263027730003787776
Offset: 0

Views

Author

N. J. A. Sloane, Nov 09 2013

Keywords

Comments

A k-packed matrix of size n X n is a matrix with entries in the alphabet A_k = {0,1, ..., k} such that each row and each column contains at least one nonzero entry.

Crossrefs

Row sums of A230878.

Programs

  • Mathematica
    p[k_, n_] := Sum[(-1)^(i + j)*Binomial[n, i]*Binomial[n, j]*(k + 1)^(i*j), {i, 0, n}, {j, 0, n}];
    a[n_] := p[2, n];
    Table[a[n], {n, 0, 10}] (* Jean-François Alcover, Oct 08 2017, translated from PARI *)
  • PARI
    \\ here p(k,n) is number of k-packed matrices of size n.
    p(k,n)={sum(i=0, n, sum(j=0, n, (-1)^(i+j) * binomial(n,i) * binomial(n,j) * (k+1)^(i*j)))}
    a(n) = p(2,n); \\ Andrew Howroyd, Sep 20 2017

Formula

Cheballah et al. give an explicit formula.
a(n) = Sum_{i=0..n} Sum_{j=0..n} (-1)^(i+j) * binomial(n,i) * binomial(n,j) * 3^(i*j). - Andrew Howroyd, Sep 20 2017

Extensions

Terms a(7) and beyond from Andrew Howroyd, Sep 20 2017

A230880 Number of 2-packed matrices with exactly n nonzero entries.

Original entry on oeis.org

1, 2, 8, 80, 1120, 20544, 463744, 12422656, 384947200, 13541822464, 533049493504, 23210958688256, 1107652218822656, 57482801016422400, 3223015475535380480, 194157345516262588416, 12505948470244176953344, 857670052436844788318208, 62395270194815987194789888
Offset: 0

Views

Author

N. J. A. Sloane, Nov 09 2013

Keywords

Comments

A k-packed matrix of size n X n is a matrix with entries in the alphabet A_k = {0,1, ..., k} such that each row and each column contains at least one nonzero entry.

Crossrefs

Programs

  • Mathematica
    b[n_] := Sum[StirlingS1[n, k]*Sum[(m!)^2*StirlingS2[k, m]^2, {m, 0, k}], {k, 0, n}]/n!;
    a[n_] := 2^n*b[n];
    Table[a[n], {n, 0, 18}] (* Jean-François Alcover, Oct 08 2017, translated from PARI *)
  • PARI
    \\ here b(n) is A104602.
    b(n) = {sum(m=0, n, sum(k=0, n, stirling(n,k,1) * m!^2 * stirling(k,m,2)^2)) / n!}
    a(n) = 2^n * b(n); \\ Andrew Howroyd, Sep 20 2017

Formula

Cheballah et al. give an explicit formula.
From Andrew Howroyd, Sep 20 2017: (Start)
a(n) = Sum_{r=1..n} Sum_{i=0..r} Sum_{j=0..r} (-1)^(i+j) * binomial(r,i) * binomial(r,j) * binomial(i*j,n) * 2^n.
a(n) = 2^n * A104602(n).
(End)

Extensions

Terms a(9) and beyond from Andrew Howroyd, Sep 20 2017

A377649 Number of edge cuts in the complete bipartite graph K_n,n.

Original entry on oeis.org

1, 11, 307, 29219, 9874531, 12425270531, 60192210392707, 1137427102035774659, 84343238614611474677731, 24650360937055503837110148611, 28488029177253725394061756995395587, 130493124785564166325712467713764904289859, 2373201513573386990964332212910033418138729872611
Offset: 1

Views

Author

Eric W. Weisstein, Nov 03 2024

Keywords

Crossrefs

Cf. A005333, A048291 (edge covers), A379215.

Formula

a(n) = 2^(n^2) - A005333(n). - Andrew Howroyd, Dec 18 2024

Extensions

a(6) onwards from Andrew Howroyd, Dec 18 2024

A122801 Number of labeled bipartite graphs on 2n vertices having equal parts and no isolated vertices.

Original entry on oeis.org

1, 1, 21, 2650, 1452605, 3149738046, 26503552820514, 868081172737564500, 111606080497500509325405, 56762846667123360827351083510, 114847831981827229530824587617895286, 927685362544629192461621864598358779955500, 29976424929810726580224613882836823991388901138994
Offset: 0

Views

Author

Max Alekseyev, Sep 11 2006

Keywords

Crossrefs

Programs

  • PARI
    { A122801(n) = binomial(2*n-1,n) * sum(k=0, n, binomial(n, k) * (-1)^k * (2^(n-k)-1)^n ); }

Formula

For n>0, a(n) = A001700(n-1) * A048291(n) = A052332(2n) - A122802(2n).

Extensions

Terms a(11) and beyond from Andrew Howroyd, Nov 07 2019
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