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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A261719 Number T(n,k) of partitions of n where each part i is marked with a word of length i over a k-ary alphabet whose letters appear in alphabetical order and all k letters occur at least once in the partition; triangle T(n,k), n>=0, 0<=k<=n, read by rows.

Original entry on oeis.org

1, 0, 1, 0, 2, 3, 0, 3, 12, 10, 0, 5, 40, 81, 47, 0, 7, 104, 396, 544, 246, 0, 11, 279, 1751, 4232, 4350, 1602, 0, 15, 654, 6528, 25100, 44475, 36744, 11481, 0, 22, 1577, 23892, 136516, 369675, 512787, 352793, 95503, 0, 30, 3560, 80979, 666800, 2603670, 5413842, 6170486, 3641992, 871030
Offset: 0

Views

Author

Alois P. Heinz, Aug 29 2015

Keywords

Comments

T(n,k) is defined for n,k >= 0. The triangle contains only the terms with k<=n. T(n,k) = 0 for k>n.

Examples

			A(3,2) = 12: 3aab, 3abb, 2aa1b, 2ab1a, 2ab1b, 2bb1a, 1a1a1b, 1a1b1a, 1a1b1b, 1b1a1a, 1b1a1b, 1b1b1a.
Triangle T(n,k) begins:
  1
  0,  1;
  0,  2,    3;
  0,  3,   12,    10;
  0,  5,   40,    81,     47;
  0,  7,  104,   396,    544,    246;
  0, 11,  279,  1751,   4232,   4350,   1602;
  0, 15,  654,  6528,  25100,  44475,  36744,  11481;
  0, 22, 1577, 23892, 136516, 369675, 512787, 352793, 95503;
  ...
		

Crossrefs

Columns k=0-10 give: A000007, A000041 (for n>0), A293366, A293367, A293368, A293369, A293370, A293371, A293372, A293373, A293374.
Row sums give A035341.
Main diagonal gives A005651.
T(2n,n) gives A261732.
Cf. A060642, A261718, A261781 (same for compositions).

Programs

  • Maple
    b:= proc(n, i, k) option remember; `if`(n=0, 1, `if`(i<1, 0,
          b(n, i-1, k)+`if`(i>n, 0, b(n-i, i, k)*binomial(i+k-1, k-1))))
        end:
    T:= (n, k)-> add(b(n$2, k-i)*(-1)^i*binomial(k, i), i=0..k):
    seq(seq(T(n, k), k=0..n), n=0..10);
  • Mathematica
    b[n_, i_, k_] := b[n, i, k] = If[n == 0, 1, If[i < 1, 0, b[n, i - 1, k] + If[i > n, 0, b[n - i, i, k]*Binomial[i + k - 1, k - 1]]]]; T[n_, k_] := Sum[b[n, n, k - i]*(-1)^i*Binomial[k, i], {i, 0, k}]; Table[T[n, k], {n, 0, 10}, {k, 0, n}] // Flatten (* Jean-François Alcover, Jan 21 2017, translated from Maple *)

Formula

T(n,k) = Sum_{i=0..k} (-1)^i * C(k,i) * A261718(n,k-i).

A256155 Decimal expansion of a constant related to A074141.

Original entry on oeis.org

1, 8, 5, 6, 3, 1, 4, 6, 5, 6, 3, 6, 1, 0, 1, 1, 4, 7, 2, 7, 4, 7, 5, 3, 5, 4, 2, 3, 2, 2, 6, 9, 2, 8, 4, 0, 4, 8, 4, 2, 5, 8, 8, 5, 9, 4, 7, 2, 2, 9, 0, 7, 0, 6, 8, 2, 0, 1, 0, 2, 5, 3, 9, 0, 7, 5, 4, 7, 6, 3, 7, 5, 6, 4, 7, 4, 6, 5, 1, 0, 0, 1, 9, 7, 1, 5, 7, 0, 7, 2, 9, 6, 0, 4, 2, 1, 5, 1, 9, 3, 0, 3, 9, 4, 5, 1, 9
Offset: 2

Views

Author

Vaclav Kotesovec, Mar 16 2015

Keywords

Examples

			18.5631465636101147274753542322692840484258859472290706820102539...
		

Crossrefs

Formula

Equals limit n->infinity A074141(n) / 2^n.
Equals Product_{k>=2} 1/(1-(k+1)/2^k). - Vaclav Kotesovec, May 10 2021
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