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.

A176120 Triangle read by rows: Sum_{j=0..k} binomial(n, j)*binomial(k, j)*j!.

Original entry on oeis.org

1, 1, 2, 1, 3, 7, 1, 4, 13, 34, 1, 5, 21, 73, 209, 1, 6, 31, 136, 501, 1546, 1, 7, 43, 229, 1045, 4051, 13327, 1, 8, 57, 358, 1961, 9276, 37633, 130922, 1, 9, 73, 529, 3393, 19081, 93289, 394353, 1441729, 1, 10, 91, 748, 5509, 36046, 207775, 1047376, 4596553, 17572114
Offset: 0

Views

Author

Roger L. Bagula, Apr 09 2010

Keywords

Comments

The number of ways of placing any number k = 0, 1, ..., min(n,m) of non-attacking rooks on an n X m chessboard. - R. J. Mathar, Dec 19 2014
Let a be a partial permutation in S the symmetric inverse semigroup on [n] with rank(a) := |image(a)| = m. Then T(n,m) = |aS| where |aS| is the size of the principal right ideal generated by a. - Geoffrey Critzer, Dec 21 2021

Examples

			Triangle begins
  1;
  1,  2;
  1,  3,   7;
  1,  4,  13,   34;
  1,  5,  21,   73,  209;
  1,  6,  31,  136,  501,  1546;
  1,  7,  43,  229, 1045,  4051,  13327;
  1,  8,  57,  358, 1961,  9276,  37633,  130922;
  1,  9,  73,  529, 3393, 19081,  93289,  394353,  1441729;
  1, 10,  91,  748, 5509, 36046, 207775, 1047376,  4596553, 17572114;
  1, 11, 111, 1021, 8501, 63591, 424051, 2501801, 12975561, 58941091, 234662231;
		

References

  • O. Ganyushkin and V. Mazorchuk, Classical Finite Transformation Semigroups, Springer, 2009, page 46.

Crossrefs

Cf. A086885 (table without column 0), A129833 (row sums).

Programs

  • Magma
    A176120:=func< n,k| (&+[Factorial(j)*Binomial(n,j)*Binomial(k,j): j in [0..k]]) >;
    [A176120(n,k): k in [0..n], n in [0..12]]; // G. C. Greubel, Aug 11 2022
    
  • Maple
    A176120 := proc(i,j)
            add(binomial(i,k)*binomial(j,k)*k!,k=0..j) ;
    end proc: # R. J. Mathar, Jul 28 2016
  • Mathematica
    T[n_, m_]:= T[n,m]= Sum[Binomial[n, k]*Binomial[m, k]*k!, {k, 0, m}];
    Table[T[n, m], {n,0,12}, {m,0,n}]//Flatten
  • SageMath
    def A176120(n,k): return sum(factorial(j)*binomial(n,j)*binomial(k,j) for j in (0..k))
    flatten([[A176120(n,k) for k in (0..n)] for n in (0..12)]) # G. C. Greubel, Aug 11 2022

Formula

Sum_{k=0..n} T(n, k) = A129833(n).
T(n,m) = A088699(n, m). - Peter Bala, Aug 26 2013
T(n,m) = A086885(n, m). - R. J. Mathar, Dec 19 2014
From G. C. Greubel, Aug 11 2022: (Start)
T(n, k) = Hypergeometric2F1([-n, -k], [], 1).
T(2*n, n) = A082545(n).
T(2*n+1, n) = A343832(n).
T(n, n) = A002720(n).
T(n, n-1) = A000262(n), n >= 1.
T(n, 1) = A000027(n+1).
T(n, 2) = A002061(n+1).
T(n, 3) = A135859(n+1). (End)

A293985 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where column k is the expansion of e.g.f. exp(x/(1-x))/(1-x)^k.

Original entry on oeis.org

1, 1, 1, 1, 2, 3, 1, 3, 7, 13, 1, 4, 13, 34, 73, 1, 5, 21, 73, 209, 501, 1, 6, 31, 136, 501, 1546, 4051, 1, 7, 43, 229, 1045, 4051, 13327, 37633, 1, 8, 57, 358, 1961, 9276, 37633, 130922, 394353, 1, 9, 73, 529, 3393, 19081, 93289, 394353, 1441729, 4596553
Offset: 0

Views

Author

Seiichi Manyama, Oct 21 2017

Keywords

Examples

			Square array begins:
    1,    1,    1,    1,     1, ... A000012;
    1,    2,    3,    4,     5, ... A000027;
    3,    7,   13,   21,    31, ... A002061;
   13,   34,   73,  136,   229, ... A135859;
   73,  209,  501, 1045,  1961, ...
  501, 1546, 4051, 9276, 19081, ...
Antidiagonal rows begin as:
  1;
  1, 1;
  1, 2,  3;
  1, 3,  7, 13;
  1, 4, 13, 34,  73;
  1, 5, 21, 73, 209, 501; - _G. C. Greubel_, Mar 09 2021
		

Crossrefs

Columns k=0..6 give: A000262, A002720, A000262(n+1), A052852(n+1), A062147, A062266, A062192.
Main diagonal gives A152059.
Similar table: A086885, A088699, A176120.

Programs

  • Magma
    function t(n,k)
      if n eq 0 then return 1;
      else return Factorial(n-1)*(&+[(j+k)*t(n-j,k)/Factorial(n-j): j in [1..n]]);
      end if; return t;
    end function;
    [t(k,n-k): k in [0..n], n in [0..12]]; // G. C. Greubel, Mar 09 2021
  • Mathematica
    t[n_, k_]:= t[n, k]= If[n==0, 1, (n-1)!*Sum[(j+k)*t[n-j,k]/(n-j)!, {j,n}]];
    T[n_,k_]:= t[k,n-k]; Table[T[n,k], {n,0,12}, {k,0,n}]//Flatten (* G. C. Greubel, Mar 09 2021 *)
  • Sage
    @CachedFunction
    def t(n,k): return 1 if n==0 else factorial(n-1)*sum( (j+k)*t(n-j,k)/factorial(n-j) for j in (1..n) )
    def T(n,k): return t(k,n-k)
    flatten([[T(n,k) for k in (0..n)] for n in (0..12)]) # G. C. Greubel, Mar 09 2021
    

Formula

A(0,k) = 1 and A(n,k) = (n-1)! * Sum_{j=1..n} (j+k)*A(n-j,k)/(n-j)! for n > 0.
A(0,k) = 1, A(1,k) = k+1 and A(n,k) = (2*n-1+k)*A(n-1,k) - (n-1)*(n-2+k)*A(n-2,k) for n > 1.
From Seiichi Manyama, Jan 25 2025: (Start)
A(n,k) = n! * Sum_{j=0..n} binomial(n+k-1,j)/(n-j)!.
A(n,k) = n! * LaguerreL(n, k-1, -1). (End)

A093190 Array t read by antidiagonals: number of {112,212}-avoiding words.

Original entry on oeis.org

1, 1, 2, 1, 4, 3, 1, 6, 9, 4, 1, 8, 21, 16, 5, 1, 10, 39, 52, 25, 6, 1, 12, 63, 136, 105, 36, 7, 1, 14, 93, 292, 365, 186, 49, 8, 1, 16, 129, 544, 1045, 816, 301, 64, 9, 1, 18, 171, 916, 2505, 3006, 1603, 456, 81, 10, 1, 20, 219, 1432, 5225, 9276, 7315, 2864, 657, 100, 11
Offset: 1

Views

Author

Ralf Stephan, Apr 20 2004

Keywords

Comments

t(k,n) = number of n-long k-ary words that simultaneously avoid the patterns 112 and 212.

Examples

			Square array begins as:
  1  1   1   1    1    1 ... 1*A000012;
  2  4   6   8   10   12 ... 2*A000027;
  3  9  21  39   63   93 ... 3*A002061;
  4 16  52 136  292  544 ... 4*A135859;
  5 25 105 365 1045 2505 ... ;
Antidiagonal rows begins as:
  1;
  1,  2;
  1,  4,  3;
  1,  6,  9,   4;
  1,  8, 21,  16,   5;
  1, 10, 39,  52,  25,  6;
  1, 12, 63, 136, 105, 36, 7;
		

Crossrefs

Main diagonal is A052852.
Antidiagonal sums are in A084261 - 1.

Programs

  • Magma
    [(&+[Factorial(j)*Binomial(k,j)*Binomial(n-k,j-1): j in [0..n-k+1]]): k in [1..n], n in [1..12]]; // G. C. Greubel, Mar 09 2021
  • Mathematica
    T[n_, k_]:= Sum[j!*Binomial[k, j]*Binomial[n-k, j-1], {j,0,n-k+1}];
    Table[T[n, k], {n,12}, {k,n}]//Flatten (* G. C. Greubel, Mar 09 2021 *)
  • PARI
    t(n,k)=sum(j=0,k,j!*binomial(k,j)*binomial(n-1,j-1))
    
  • Sage
    flatten([[ sum(factorial(j)*binomial(k,j)*binomial(n-k,j-1) for j in (0..n-k+1)) for k in (1..n)] for n in (1..12)]) # G. C. Greubel, Mar 09 2021
    

Formula

t(n, k) = Sum{j=0..n} j!*C(n, j)*C(k-1, j-1). (square array)
T(n, k) = Sum_{j=0..n-k+1} j!*binomial(k,j)*binomial(n-k,j-1). (number triangle) - G. C. Greubel, Mar 09 2021

A135858 A128229^2 * A000012.

Original entry on oeis.org

1, 3, 1, 7, 5, 1, 13, 13, 7, 1, 21, 21, 21, 9, 1, 31, 31, 31, 31, 11, 1, 43, 43, 43, 43, 43, 13, 1, 57, 57, 57, 57, 57, 57, 15, 1, 73, 73, 73, 73, 73, 73, 73, 17, 1, 91, 91, 91, 91, 91, 91, 91, 91, 19, 1
Offset: 1

Views

Author

Gary W. Adamson, Dec 01 2007

Keywords

Comments

Row sums = A135859: (1, 4, 13, 34, 73, 136, ...).

Examples

			First few rows of the triangle:
   1;
   3,  1;
   7,  5,  1;
  13, 13,  7,  1;
  21, 21, 21,  9,  1;
  31, 31, 31, 31, 11,  1;
  43, 43, 43, 43, 43, 13, 1;
  ...
		

Crossrefs

Formula

A128229^2 * A000012, where A128229 = a bidiagonal matrix with all 1's in the main diagonal and (1, 2, 3, ...) in the subdiagonal.
Showing 1-4 of 4 results.