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.

A327584 Number T(n,k) of colored compositions of n using all colors of a k-set such that all parts have different color patterns and the patterns for parts i have i distinct colors in increasing order; triangle T(n,k), k>=0, k<=n<=k*2^(k-1), read by columns.

Original entry on oeis.org

1, 1, 3, 4, 6, 13, 48, 150, 300, 666, 936, 1824, 2520, 2160, 5040, 75, 536, 2820, 11144, 41346, 131304, 420084, 1191552, 3427008, 9207456, 23466720, 61522560, 141553560, 345346560, 777152160, 1635096960, 3700806480, 6998261760, 14211912960, 27442437120
Offset: 0

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Author

Alois P. Heinz, Sep 17 2019

Keywords

Comments

T(n,k) is defined for all n>=0 and k>=0. The triangle displays only positive terms. All other terms are zero.

Examples

			T(3,2) = 4: 2ab1a, 2ab1b, 1a2ab, 1b2ab.
T(3,3) = 13: 3abc, 2ab1c, 2ac1b, 2bc1a, 1a2bc, 1b2ac, 1c2ab, 1a1b1c, 1a1c1b, 1b1a1c, 1b1c1a, 1c1a1b, 1c1b1a.
T(4,2) = 6: 2ab1a1b, 1a2ab1b, 1a1b2ab, 2ab1b1a, 1b2ab1a, 1b1a2ab.
Triangle T(n,k) begins:
  1;
     1;
        3;
        4,  13;
        6,  48,    75;
           150,   536,    541;
           300,  2820,   6320,   4683;
           666, 11144,  50150,  81012,   47293;
           936, 41346, 308080, 903210, 1134952, 545835;
           ...
		

Crossrefs

Main diagonal gives A000670.
Row sums give A321587.
Column sums give A327585.
Cf. A001787, A326962, A327583 (this triangle read by rows).

Programs

  • Maple
    C:= binomial:
    g:= proc(n) option remember; n*2^(n-1) end:
    h:= proc(n) option remember; local k; for k from
          `if`(n=0, 0, h(n-1)) do if g(k)>=n then return k fi od
        end:
    b:= proc(n, i, k, p) option remember; `if`(n=0, p!,
          `if`(i<1 or k add(b(n$2, i, 0)*(-1)^(k-i)*C(k, i), i=0..k):
    seq(seq(T(n, k), n=k..k*2^(k-1)), k=0..5);
  • Mathematica
    c = Binomial;
    g[n_] := g[n] = n*2^(n - 1);
    h[n_] := h[n] = Module[{k}, For[k = If[n == 0, 0,
         h[n - 1]], True, k++, If[g[k] >= n, Return[k]]]];
    b[n_, i_, k_, p_] := b[n, i, k, p] = If[n == 0, p!,
         If[i < 1 || k < h[n], 0, Sum[b[n - i*j, Min[n - i*j, i - 1],
         k, p + j]*c[c[k, i], j], {j, 0, n/i}]]];
    T[n_, k_] := Sum[b[n, n, i, 0]*(-1)^(k - i)*c[k, i], {i, 0, k}];
    Table[Table[T[n, k], {n, k, k*2^(k - 1)}], {k, 0, 5}] // Flatten (* Jean-François Alcover, Feb 22 2021, after Alois P. Heinz *)