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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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)

A094525 Square array of binomial transforms read by antidiagonals.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 3, 3, 1, 1, 4, 7, 4, 1, 1, 5, 13, 13, 5, 1, 1, 6, 21, 28, 21, 6, 1, 1, 7, 31, 49, 49, 31, 7, 1, 1, 8, 43, 76, 89, 76, 43, 8, 1, 1, 9, 57, 109, 141, 141, 109, 57, 9, 1, 1, 10, 73, 148, 205, 226, 205, 148, 73, 10, 1, 11, 91, 193, 281
Offset: 0

Views

Author

Paul Barry, May 07 2004

Keywords

Comments

Rows (and columns) are binomial transforms of [1,k,k(k-1),0,0,0,...], k>=0. One of a family of arrays that converge to A088699.

Examples

			Rows start
1,1,1,1,1,...
1,2,3,4,5,...
1,3,7,13,21,...
1,4,13,28,29,...
1,5,21,49,89,...
		

Crossrefs

Cf. A094526.

Formula

Square array T(n, k) defined by T(n, k)=1+kn+k(k-1)n(n-1)/2

A094526 Square array of binomial transforms read by antidiagonals.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 3, 3, 1, 1, 4, 7, 4, 1, 1, 5, 13, 13, 5, 1, 1, 6, 21, 34, 21, 6, 1, 1, 7, 31, 73, 73, 31, 7, 1, 1, 8, 43, 136, 185, 136, 43, 8, 1, 1, 9, 57, 229, 381, 381, 229, 57, 9, 1, 1, 10, 73, 358, 685, 826, 685, 358, 73, 10, 1, 1, 11, 91, 529, 1121, 1531
Offset: 0

Views

Author

Paul Barry, May 07 2004

Keywords

Comments

Rows (and columns) are binomial transforms of [1,k,k(k-1),k(k-1)(k-2),0,0,...], k>=0. One of a family of arrays that converge to A088699.

Examples

			Rows start
1,1,1,1,1,...
1,2,3,4,5,...
1,3,7,13,21,...
1,4,13,34,73,...
1,5,21,73,185,...
		

Crossrefs

Cf. A094525.

Formula

Square array T(n, k) defined by T(n, k)=1+kn+k(k-1)n(n-1)/2+k(k-1)(k-2)n(n-1)(n-2)/6

A329655 Square array read by antidiagonals: T(n,k) is the number of relations between set A with n elements and set B with k elements that are both right unique and left unique.

Original entry on oeis.org

1, 2, 2, 3, 6, 3, 4, 12, 12, 4, 5, 20, 33, 20, 5, 6, 30, 72, 72, 30, 6, 7, 42, 135, 208, 135, 42, 7, 8, 56, 228, 500, 500, 228, 56, 8, 9, 72, 357, 1044, 1545, 1044, 357, 72, 9, 10, 90, 528, 1960, 4050, 4050, 1960, 528, 90, 10, 11, 110, 747, 3392, 9275, 13326, 9275, 3392, 747, 110, 11
Offset: 1

Views

Author

Roy S. Freedman, Nov 18 2019

Keywords

Comments

A relation R between set A with n elements and set B with k elements is a subset of the Cartesian product A x B. A relation R is right unique if (a, b1) in R and (a,b2) in R implies b1=b2. A relation R is left unique if (a1,b) in R and (a2,b) in R implies a1=a2.

Examples

			The symmetric array T(n,k) begins:
  1,   2,    3,    4,     5,      6,       7,       8,        9, ...
  2,   6,   12,   20,    30,     42,      56,      72,       90, ...
  3,  12,   33,   72,   135,    228,     357,     528,      747, ...
  4,  20,   72,  208,   500,   1044,    1960,    3392,     5508, ...
  5,  30,  135,  500,  1545,   4050,    9275,   19080,    36045, ...
  6,  42,  228, 1044,  4050,  13326,   37632,   93288,   207774, ...
  7,  56,  357, 1960,  9275,  37632,  130921,  394352,  1047375, ...
  8,  72,  528, 3392, 19080,  93288,  394352, 1441728,  4596552, ...
  9,  90,  747, 5508, 36045, 207774, 1047375, 4596552, 17572113, ...
		

Crossrefs

The diagonal T(n,n) is A097662. T(1,k)=A000027; T(2,k)=A002378; T(3,k)=A054602.

Programs

  • Maple
    T:= (n,k)-> value(Sum(binomial(n,j)*binomial(k, j)*j!, j=1..k)):
    seq(seq(T(n, 1+d-n), n=1..d), d=1..12);
  • Mathematica
    T[n_, k_] := Sum[Binomial[n, j] * Binomial[k, j] * j!, {j, 1, k}]; Table[T[n - k + 1, k], {n, 1, 11}, {k, 1, n}] // Flatten (* Amiram Eldar, Nov 25 2019 *)
  • MuPAD
    T:=(n,k)->_plus (binomial(n,j)*binomial(k, j)* j! $ j=1..k):

Formula

T(n,k) = Sum_{j=1..k} binomial(n,j)*binomial(k,j)*j!.
T(n,k) = A088699(n,k)-1.
Previous Showing 11-14 of 14 results.