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 1-5 of 5 results.

A049311 Number of (0,1) matrices with n ones and no zero rows or columns, up to row and column permutations.

Original entry on oeis.org

1, 3, 6, 16, 34, 90, 211, 558, 1430, 3908, 10725, 30825, 90156, 273234, 848355, 2714399, 8909057, 30042866, 103859678, 368075596, 1335537312, 4958599228, 18820993913, 72980867400, 288885080660, 1166541823566, 4802259167367, 20141650236664
Offset: 1

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Author

Keywords

Comments

Also the number of bipartite graphs with n edges, no isolated vertices and a distinguished bipartite block, up to isomorphism.
The EULERi transform (A056156) is also interesting.
a(n) is also the number of non-isomorphic set multipartitions (multisets of sets) of weight n. - Gus Wiseman, Mar 17 2017

Examples

			E.g. a(2) = 3: two ones in same row, two ones in same column, or neither.
a(3) = 6 is coefficient of x^3 in (1/36)*((1 + x)^9 + 6*(1 + x)^3*(1 + x^2)^3 + 8*(1 + x^3)^3 + 9*(1 + x)*(1 + x^2)^4 + 12*(1 + x^3)*(1 + x^6))=1 + x + 3*x^2 + 6*x^3 + 7*x^4 + 7*x^5 + 6*x^6 + 3*x^7 + x^8 + x^9.
There are a(3) = 6 binary matrices with 3 ones, with no zero rows or columns, up to row and column permutation:
  [1 0 0] [1 1 0] [1 0] [1 1] [1 1 1] [1]
  [0 1 0] [0 0 1] [1 0] [1 0] ....... [1].
  [0 0 1] ....... [0 1] ............. [1]
Non-isomorphic representatives of the a(3)=6 set multipartitions are: ((123)), ((1)(23)), ((2)(12)), ((1)(1)(1)), ((1)(2)(2)), ((1)(2)(3)). - _Gus Wiseman_, Mar 17 2017
		

Crossrefs

Programs

  • PARI
    WeighT(v)={Vec(exp(x*Ser(dirmul(v, vector(#v,n,(-1)^(n-1)/n))))-1,-#v)}
    permcount(v) = {my(m=1, s=0, k=0, t); for(i=1, #v, t=v[i]; k=if(i>1&&t==v[i-1], k+1, 1); m*=t*k; s+=t); s!/m}
    K(q, t, k)={WeighT(Vec(sum(j=1, #q, gcd(t, q[j])*x^lcm(t, q[j])) + O(x*x^k), -k))}
    a(n)={my(s=0); forpart(q=n, s+=permcount(q)*polcoef(exp(x*Ser(sum(t=1, n, K(q, t, n)/t))), n)); s/n!} \\ Andrew Howroyd, Jan 16 2023

Formula

Calculate number of connected bipartite graphs + number of connected bipartite graphs with no duality automorphism, then apply EULER transform.
a(n) is the coefficient of x^n in the cycle index Z(S_n X S_n; 1+x, 1+x^2, ...), where S_n X S_n is Cartesian product of symmetric groups S_n of degree n.

Extensions

More terms and formula from Vladeta Jovovic, Jul 29 2000
a(19)-a(28) from Max Alekseyev, Jul 22 2009
a(29)-a(102) from Aliaksandr Siarhei, Dec 13 2013
Name edited by Gus Wiseman, Dec 18 2018

A057150 Triangle read by rows: T(n,k) = number of k X k binary matrices with n ones, 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, 0, 5, 2, 1, 0, 0, 4, 11, 2, 1, 0, 0, 3, 21, 14, 2, 1, 0, 0, 1, 34, 49, 15, 2, 1, 0, 0, 1, 33, 131, 69, 15, 2, 1, 0, 0, 0, 33, 248, 288, 79, 15, 2, 1, 0, 0, 0, 19, 410, 840, 420, 82, 15, 2, 1, 0, 0, 0, 14, 531, 2144, 1744, 497, 83, 15, 2, 1
Offset: 1

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Author

Vladeta Jovovic, Aug 14 2000

Keywords

Comments

Also the number of non-isomorphic set multipartitions (multisets of sets) of weight n with k parts and k vertices. - Gus Wiseman, Nov 14 2018

Examples

			[1], [0,1], [0,1,1], [0,1,2,1], [0,0,5,2,1], [0,0,4,11,2,1], ...;
There are 8 square binary matrices with 5 ones, with no zero rows or columns, up to row and column permutation: 5 of size 3 X 3:
[0 0 1] [0 0 1] [0 0 1] [0 0 1] [0 0 1]
[0 0 1] [0 1 0] [0 1 1] [0 1 1] [1 1 0]
[1 1 1] [1 1 1] [1 0 1] [1 1 0] [1 1 0]
2 of size 4 X 4:
[0 0 0 1] [0 0 0 1]
[0 0 0 1] [0 0 1 0]
[0 0 1 0] [0 1 0 0]
[1 1 0 0] [1 0 0 1]
and 1 of size 5 X 5:
[0 0 0 0 1]
[0 0 0 1 0]
[0 0 1 0 0]
[0 1 0 0 0]
[1 0 0 0 0].
From _Gus Wiseman_, Nov 14 2018: (Start)
Triangle begins:
   1
   0   1
   0   1   1
   0   1   2   1
   0   0   5   2   1
   0   0   4  11   2   1
   0   0   3  21  14   2   1
   0   0   1  34  49  15   2   1
   0   0   1  33 131  69  15   2   1
   0   0   0  33 248 288  79  15   2   1
Non-isomorphic representatives of the multiset partitions counted in row 6 {0,0,4,11,2,1} are:
  {{12}{13}{23}}  {{1}{1}{1}{234}}  {{1}{2}{3}{3}{45}}  {{1}{2}{3}{4}{5}{6}}
  {{1}{23}{123}}  {{1}{1}{24}{34}}  {{1}{2}{3}{5}{45}}
  {{13}{23}{23}}  {{1}{1}{4}{234}}
  {{3}{23}{123}}  {{1}{2}{34}{34}}
                  {{1}{3}{24}{34}}
                  {{1}{3}{4}{234}}
                  {{1}{4}{24}{34}}
                  {{1}{4}{4}{234}}
                  {{2}{4}{12}{34}}
                  {{3}{4}{12}{34}}
                  {{4}{4}{12}{34}}
(End)
		

Crossrefs

Programs

  • Mathematica
    permcount[v_List] := Module[{m = 1, s = 0, k = 0, t}, For[i = 1, i <= Length[v], i++, t = v[[i]]; k = If[i > 1 && t == v[[i - 1]], k + 1, 1]; m *= t*k; s += t]; s!/m];
    c[p_List, q_List, k_] := SeriesCoefficient[Product[Product[(1 + O[x]^(k + 1) + x^LCM[p[[i]], q[[j]]])^GCD[p[[i]], q[[j]]], {j, 1, Length[q]}], {i, 1, Length[p]}], {x, 0, k}];
    M[m_, n_, k_] := M[m, n, k] = Module[{s = 0}, Do[Do[s += permcount[p]* permcount[q]*c[p, q, k], {q, IntegerPartitions[n]}], {p, IntegerPartitions[m]}]; s/(m!*n!)];
    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, 12}, {k, 1, n}] // Flatten (* Jean-François Alcover, Sep 10 2019, after Andrew Howroyd *)
  • PARI
    \\ See A321609 for M.
    T(n,k) = M(k,k,n) - 2*M(k,k-1,n) + M(k-1,k-1,n); \\ Andrew Howroyd, Nov 14 2018

Extensions

Duplicate seventh row removed by Gus Wiseman, Nov 14 2018

A053304 Number of 7 X 7 binary matrices with n=0..49 ones up to row and column permutations.

Original entry on oeis.org

1, 1, 3, 6, 16, 34, 90, 211, 515, 1229, 2960, 6893, 15753, 34450, 72235, 143477, 269186, 473945, 781713, 1203617, 1728192, 2310376, 2874232, 3325215, 3576980, 3576980, 3325215, 2874232, 2310376, 1728192, 1203617, 781713, 473945, 269186
Offset: 0

Views

Author

Vladeta Jovovic, Mar 05 2000

Keywords

Crossrefs

Row 7 of A052371 and A321609.

Programs

  • PARI
    \\ See A321609 for M.
    vector(50, n, M(7,7,n-1))

Formula

a(n) = A049311(n) for n <= 7.
Sum_{n=0..49} a(n) = 33642660 = A002724(7).

A053305 Number of 8 X 8 binary matrices with n=0..64 ones up to row and column permutations.

Original entry on oeis.org

1, 1, 3, 6, 16, 34, 90, 211, 558, 1371, 3601, 9209, 24110, 61740, 157559, 390832, 946490, 2206364, 4948194, 10591141, 21606125, 41821936, 76738813, 133157386, 218402867, 338187004, 494330780, 681660841, 886842587, 1088201827
Offset: 0

Views

Author

Vladeta Jovovic, Mar 05 2000

Keywords

Crossrefs

Row 8 of A052371 and A321609.

Programs

  • PARI
    \\ See A321609 for M.
    vector(65, n, M(8, 8, n-1))

Formula

a(n) = A049311(n) for n <= 8.
Sum_{n=0..64} a(n) = 14685630688 = A002724(8).

A334550 Triangle read by rows: T(n,k) is the number of binary matrices with n ones, k columns and no zero rows or columns, up to permutations of rows and columns.

Original entry on oeis.org

1, 1, 2, 1, 2, 3, 1, 5, 5, 5, 1, 5, 12, 9, 7, 1, 9, 23, 29, 17, 11, 1, 9, 39, 62, 57, 28, 15, 1, 14, 63, 147, 154, 110, 47, 22, 1, 14, 102, 278, 409, 329, 194, 73, 30, 1, 20, 150, 568, 991, 1023, 664, 335, 114, 42, 1, 20, 221, 1020, 2334, 2844, 2267, 1243, 549, 170, 56
Offset: 1

Views

Author

Andrew Howroyd, Jul 03 2020

Keywords

Comments

T(n,k) is also the number of non-isomorphic set multipartitions (multisets of sets) of weight n with k parts.

Examples

			Triangle begins:
  1;
  1,  2;
  1,  2,  3;
  1,  5,  5,   5;
  1,  5, 12,   9,   7;
  1,  9, 23,  29,  17,  11;
  1,  9, 39,  62,  57,  28, 15;
  1, 14, 63, 147, 154, 110, 47, 22;
  ...
The T(4,3) = 5 matrices are:
  [1 0 0]   [1 0 0]   [1 1 0]   [1 1 1]   [1 1 0]
  [1 0 0]   [1 0 0]   [1 0 0]   [1 0 0]   [1 0 1]
  [0 1 0]   [0 1 1]   [0 0 1]
  [0 0 1]
The T(4,3) = 5 the set multipartitions are:
  {{1,2}, {3}, {4}},
  {{1,2}, {3}, {3}},
  {{1,2}, {1}, {3}},
  {{1,2}, {1}, {1}},
  {{1,2}, {1}, {2}}.
		

Crossrefs

Row sums are A049311.
Main diagonal is A000041.

Programs

  • PARI
    \\ See A321609 for definition of M.
    T(n, k)={M(k, n, n) - M(k-1, n, n)}
    for(n=1, 10, for(k=1, n, print1(T(n, k), ", ")); print)
    
  • PARI
    \\ Faster version.
    permcount(v) = {my(m=1, s=0, k=0, t); for(i=1, #v, t=v[i]; k=if(i>1&&t==v[i-1], k+1, 1); m*=t*k; s+=t); s!/m}
    K(q, t, n)={prod(j=1, #q, (1+x^lcm(t, q[j]) + O(x*x^n))^gcd(t, q[j]))}
    G(m,n)={my(s=0); forpart(q=m, s+=permcount(q)*exp(sum(t=1, n, (K(q, t, n)-1)/t) + O(x*x^n))); s/m!}
    A(n,m=n)={my(p=sum(k=0, m, G(k,n)*y^k)*(1-y)); matrix(n, m, n, k, polcoef(polcoef(p, n, x), k, y))}
    { my(T=A(10)); for(n=1, #T, print(T[n,1..n])) }
Showing 1-5 of 5 results.