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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.

A327117 Number T(n,k) of colored integer partitions of n using all colors of a k-set such that a color pattern for part i has i distinct colors in increasing order; triangle T(n,k), n>=0, 0<=k<=n, read by rows.

Original entry on oeis.org

1, 0, 1, 0, 1, 2, 0, 1, 4, 5, 0, 1, 7, 18, 15, 0, 1, 10, 45, 84, 52, 0, 1, 14, 94, 298, 415, 203, 0, 1, 18, 174, 844, 1995, 2178, 877, 0, 1, 23, 300, 2081, 7440, 13638, 12131, 4140, 0, 1, 28, 486, 4652, 23670, 64898, 95823, 71536, 21147, 0, 1, 34, 756, 9682, 67390, 259599, 566447, 694676, 445356, 115975
Offset: 0

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Author

Alois P. Heinz, Sep 13 2019

Keywords

Comments

The sequence of column k satisfies a linear recurrence with constant coefficients of order k*2^(k-1) = A001787(k).

Examples

			T(3,2) = 4: 2ab1a, 2ab1b, 1a1a1b, 1a1b1b.
Triangle T(n,k) begins:
  1;
  0, 1;
  0, 1,  2;
  0, 1,  4,   5;
  0, 1,  7,  18,   15;
  0, 1, 10,  45,   84,    52;
  0, 1, 14,  94,  298,   415,    203;
  0, 1, 18, 174,  844,  1995,   2178,    877;
  0, 1, 23, 300, 2081,  7440,  13638,  12131,   4140;
  0, 1, 28, 486, 4652, 23670,  64898,  95823,  71536,  21147;
  0, 1, 34, 756, 9682, 67390, 259599, 566447, 694676, 445356, 115975;
  ...
		

Crossrefs

Columns k=0-3 give: A000007, A057427, A014616(n-1) for n>1, A327842.
Main diagonal gives A000110.
Row sums give A116540.
T(2n,n) gives A327843.

Programs

  • Maple
    C:= binomial:
    b:= proc(n, i, k) option remember; `if`(n=0, 1, `if`(i<1, 0, add(
          b(n-i*j, min(n-i*j, i-1), k)*C(C(k, i)+j-1, j), j=0..n/i)))
        end:
    T:= (n, k)-> add(b(n$2, i)*(-1)^(k-i)*C(k, i), i=0..k):
    seq(seq(T(n, k), k=0..n), n=0..12);
  • Mathematica
    b[n_, i_, k_] := b[n, i, k] = If[n == 0, 1, If[i<1, 0, Sum[b[n - i j, Min[n - i j, i - 1], k] Binomial[Binomial[k, i] + j - 1, j], {j, 0, n/i}]]];
    T[n_, k_] := Sum[b[n, n, i] (-1)^(k - i) Binomial[k, i], {i, 0, k}];
    Table[T[n, k], {n, 0, 12}, {k, 0, n}] // Flatten (* Jean-François Alcover, Oct 04 2019, after Alois P. Heinz *)

Formula

Sum_{k=1..n} k * T(n,k) = A327118(n).