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 1-3 of 3 results.

A178962 Partial sums of A007322.

Original entry on oeis.org

1, 7, 46, 366, 3647, 44205, 630956, 10350572, 191704349, 3954598099, 89888942874, 2231742720730, 60083847852539, 1743321481158041, 54226970410827160, 1800062257926566488, 63512168752599139129, 2373501269897667585631
Offset: 1

Views

Author

Jonathan Vos Post, Dec 31 2010

Keywords

Examples

			a(3) = 1 + 6 + 39 = 46.
		

Crossrefs

Formula

a(n) = Sum_{i=1..n} Sum_{r>=0,s>=0} binomial(r*s+i-1,i)/2^(r+s+2).

A120733 Number of matrices with nonnegative integer entries and without zero rows or columns such that sum of all entries is equal to n.

Original entry on oeis.org

1, 1, 5, 33, 281, 2961, 37277, 546193, 9132865, 171634161, 3581539973, 82171451025, 2055919433081, 55710251353953, 1625385528173693, 50800411296363617, 1693351638586070209, 59966271207156833313, 2248276994650395873861, 88969158875611127548481
Offset: 0

Views

Author

Vladeta Jovovic, Aug 18 2006, Aug 21 2006

Keywords

Comments

The number of such matrices up to rows/columns permutations are given in A007716.
Dimensions of the graded components of the Hopf algebra MQSym (Matrix quasi-symmetric functions). - Jean-Yves Thibon (jyt(AT)univ-mlv.fr), Oct 23 2006
From Kyle Petersen, Aug 10 2016: (Start)
Number of cells in the two-sided Coxeter complex of the symmetric group. Inclusion of faces corresponds to refinement of matrices, see Section 6 of Petersen paper. The number of cells in the type B analog is given by A275787.
Also known as "two-way contingency tables" in the Diaconis-Gangolli reference. (End)

Examples

			a(2) = 5:
[1 0]   [0 1]   [1]   [1 1]   [2]
[0 1]   [1 0]   [1]
From _Gus Wiseman_, Nov 14 2018: (Start)
The a(3) = 33 matrices:
  [3][21][12][111]
.
  [2][20][11][11][110][101][1][10][10][100][02][011][01][01][010][001]
  [1][01][10][01][001][010][2][11][02][011][10][100][20][11][101][110]
.
  [1][10][10][10][100][100][01][01][010][01][010][001][001]
  [1][10][01][01][010][001][10][10][100][01][001][100][010]
  [1][01][10][01][001][010][10][01][001][10][100][010][100]
(End)
		

Crossrefs

Row sums of A261781.

Programs

  • Maple
    t1 := M -> add( add( add( (-1)^(n-j)*binomial(n, j)*((1-x)^(-j)-1)^m, j=0..n), n=0..M), m=0..M); s := series(t1(20),x,20); gfun[seriestolist](%); # N. J. A. Sloane, Jan 14 2009
  • Mathematica
    a[n_] := Sum[2^(-2-r-s)*Binomial[n+r*s-1, n], {r, 0, Infinity}, {s, 0, Infinity}]; Table[Print[an = a[n]]; an, {n, 0, 19}] (* Jean-François Alcover, May 15 2012, after Vladeta Jovovic *)
    Flatten[{1,Table[1/n!*Sum[(-1)^(n-k)*StirlingS1[n,k]*Sum[m!*StirlingS2[k, m],{m,k}]^2,{k,n}],{n,20}]}] (* Vaclav Kotesovec, May 07 2014 *)
    multsubs[set_,k_]:=If[k==0,{{}},Join@@Table[Prepend[#,set[[i]]]&/@multsubs[Drop[set,i-1],k-1],{i,Length[set]}]]; Table[Length[Select[multsubs[Tuples[Range[n],2],n],And[Union[First/@#]==Range[Max@@First/@#],Union[Last/@#]==Range[Max@@Last/@#]]&]],{n,5}] (* Gus Wiseman, Nov 14 2018 *)

Formula

a(n) = (1/n!)*Sum_{k=0..n} (-1)^(n-k)*Stirling1(n,k)*A000670(k)^2.
G.f.: Sum_{m>=0,n>=0} Sum_{j=0..n} (-1)^(n-j)*C(n,j)*((1-x)^(-j)-1)^m.
a(n) = Sum_{r>=0,s>=0} binomial(r*s+n-1,n)/2^(r+s+2).
G.f.: Sum_{n>=0} 1/(2-(1-x)^(-n))/2^(n+1). - Vladeta Jovovic, Oct 30 2006
a(n) ~ 2^(log(2)/2-2) * n! / (log(2))^(2*n+2). - Vaclav Kotesovec, May 07 2014

Extensions

More terms from N. J. A. Sloane, Jan 14 2009

A101370 Number of zero-one matrices with n ones and no zero rows or columns.

Original entry on oeis.org

1, 4, 24, 196, 2016, 24976, 361792, 5997872, 111969552, 2324081728, 53089540992, 1323476327488, 35752797376128, 1040367629940352, 32441861122796672, 1079239231677587264, 38151510015777089280, 1428149538870997774080, 56435732691153773665280
Offset: 1

Views

Author

Peter J. Cameron, Jan 14 2005

Keywords

Comments

a(n) = (1/(4*n!)) * Sum_{r, s>=0} (r*s)_n / 2^(r+s), where (m)_n is the falling factorial m * (m-1) * ... * (m-n+1). [Maia and Mendez]

Examples

			a(2)=4:
[1 1] [1] [1 0] [0 1]
..... [1] [0 1] [1 0]
From _Gus Wiseman_, Nov 14 2018: (Start)
The a(3) = 24 matrices:
  [111]
.
  [11][11][110][101][10][100][011][01][010][001]
  [10][01][001][010][11][011][100][11][101][110]
.
  [1][10][10][10][100][100][01][01][010][01][010][001][001]
  [1][10][01][01][010][001][10][10][100][01][001][100][010]
  [1][01][10][01][001][010][10][01][001][10][100][010][100]
(End)
		

References

  • Georg Cantor, Gesammelte Abhandlungen mathematischen und philosophischen Inhalts, p. 435 (IV, 4. Mitteilungen zur Lehre vom Transfiniten, VIII Nr. 13), Springer, Berlin. [Rainer Rosenthal, Apr 10 2007]

Crossrefs

Cf. A000670 (the sequence P(n)), A049311 (row and column permutations allowed), A120733, A122725, A135589, A283877, A321446, A321587.

Programs

  • GAP
    P:=function(n) return Sum([1..n],x->Stirling2(n,x)*Factorial(x)); end;
    
  • GAP
    F:=function(n) return Sum([1..n],x->(-1)^(n-x)*Stirling1(n,x)*P(x)^2)/Factorial(n); end;
    
  • Mathematica
    m = 17; a670[n_] = Sum[ StirlingS2[n, k]*k!, {k, 0, n}]; Rest[ CoefficientList[ Series[ Sum[ a670[n]^2*(Log[1 + x]^n/n!), {n, 0, m}], {x, 0, m}], x]] (* Jean-François Alcover, Sep 02 2011, after g.f.  *)
    Table[Length[Select[Subsets[Tuples[Range[n],2],{n}],And[Union[First/@#]==Range[Max@@First/@#],Union[Last/@#]==Range[Max@@Last/@#]]&]],{n,5}] (* Gus Wiseman, Nov 14 2018 *)
  • PARI
    {A000670(n)=sum(k=0,n,stirling(n, k,2)*k!)}
    {a(n)=polcoeff(sum(m=0,n,A000670(m)^2*log(1+x+x*O(x^n))^m/m!),n)}
    /* Paul D. Hanna, Nov 07 2009 */

Formula

a(n) = (Sum s(n, k) * P(k)^2)/n!, where P(n) is the number of labeled total preorders on {1, ..., n} (A000670), s are signed Stirling numbers of the first kind.
G.f.: Sum_{m>=0,n>=0} Sum_{j=0..n} (-1)^(n-j)*binomial(n,j)*((1+x)^j-1)^m. - Vladeta Jovovic, Mar 25 2006
Inverse binomial transform of A007322. - Vladeta Jovovic, Aug 17 2006
G.f.: Sum_{n>=0} 1/(2-(1+x)^n)/2^(n+1). - Vladeta Jovovic, Sep 23 2006
G.f.: Sum_{n>=0} A000670(n)^2*log(1+x)^n/n! where 1/(1-x) = Sum_{n>=0} A000670(n)*log(1+x)^n/n!. - Paul D. Hanna, Nov 07 2009
a(n) ~ n! / (2^(2+log(2)/2) * (log(2))^(2*(n+1))). - Vaclav Kotesovec, Dec 31 2013
Showing 1-3 of 3 results.